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Contents

• Chapter 1 - setting up your ZX interface 1

• general setup

• Chapter 2 - Setting up your microdrive

• handling cartridges
• protecting programs and data stored in cartridges
• the cartridge lifespan

• Chapter 3 - Starting with your microdrive

• auto-run
• the catalogue
• loading programs

• Chapter 4 - Programs and the microdrive

• saving, verifying, loading and merging programs
• erasing programs
• formatting and naming blank cartridges
• setting up your own auto-run facility

• Chapter 5 - Data, channels and streams

• Channels and streams

• Chapter 6 - Data and the microdrive

• opening and naming a data file
• entering data
• closing file
• reading back from a file
• note on PRINT and INPUT
• reading the file catalogue
• protecting a file
• extending a file

• Chapter 7 - The local area network

• setting up a network
• programs and the network
• data and the network
• broadcasting

• Chapter 8 - using the RS232 interface

• connecting peripherals to the RS232 interface
• t and b channels
• the t channel
• the b channel
• sending control codes

• Chapter 9 - the MOVE statement

• the printer server program

• Appendix 1 - The net game
• Appendix 2 - System variables
• Appendix 3 - Microdrive and network channels
• Appendix 4 - RS232 connections
• Appendix 5 - Reports
• Appendix 6 - The extended BASIC

Chapter 1 - Setting up your ZX interface 1

• this booklet
• the interface itself (with two captive screws on the underside)
• a ribbon cable about8cms long (for connecting the interface to a microdrive)
• a lead with a jack plug at either end (for setting up a network)

1. Unplug the computer
2. Disconnect the computer from its peripherals
3. Using a posidrive screwdriver remove the two screws on the underside of the computer
   (You will only need these screws again if you later disconnect the interface from the computer.)
4. Push the interface edge connector firmly into the socket at the back of the computer
5. Screw the interface to the underside of the computer using the two captive screws supplied.

Chapter 2 - Setting up your microdrive

• the microdrive itself
• an electrical connector (for connecting this microdrive to another one)
• a pre-recorded demonstration cartridge

To attach the microdrive to the interface, push one end of the ribbon cable (supplied with the interface) firmly into the socket on the side of the interface. Then push the other end of the cable into the socket in the side of the microdrive.

If you have several micrdrives, the second one can be connected to the first as follows.

• Disconnect the microdrive deom the computer.
• Turn both microdrives upside down. You will find that each has a bracket screwed to the underside.
• Unscrew and remove both brackets.
• Turn both microdrives the right way up.
• Push one of the electrical connectors firmly into the socket on the side of one of you microdrives.
• Push the second microdrive up agains the first, so that the other end of the electrical connector pushes into the socket on the side of the second microdrive.
• Carefully turning the microdrives over again, screw back one of the two brackets, but this time so that it links up the two microdrives. (The remaining electrical connector, bracket and screws can be kept for connecting up further microdrives.)
• Turn the microdrives the right way up again, and reconnect the one on the right-handed
end to the computer.

NOTE: the microdrive nearest the computer is always known as microdrive 1, and the next along is microdrive 2 and so on. Notice also that on the front of each microdrive there is a light which will come on whenever the microdrive is running.

Handling cartridges

Every cartridge comes in a protective box; and should always be kept in its box when not in use. When you take a cartridge out of its box (being careful not to touch the tape itself) you will see that it has a level on the top and another on the side. Push the cartridge firmly into the slot in the front of the microdrive, making sure that the label on the side faces upwards. This will leave the top of the cartridge projecting by about 1/2 cm. The microdrive and cartridge are now ready to be used.

Never take the cartridge out of the drive while the drive light is on. Never switch the power on or off while a cartridge is in the drive.

Protecting programs and data stored in cartridges

If you wish to protect the programs and data stored in a cartridge (that is, prevent them from being over-written or erased) then you should snap off the plastic tab from the side of the cartridge. (As with a cassette, you can reverse this effect by sticking some tape over the space left where the tab has been removed.)

The cartridge lifespan

Microdrive cartridges will not last forever, and will eventually need to be replaced. The symptom of an ageing cartridge is that the computer will take longer and longer to find a program or file before loading it. So it is a good idea to keep back-up copies of important programs or files either on another cartridge, or on cassette.

Starting with your microdrive

Auto-run

Now that you have setup your ZX interface 1 and your microdrive, you will want to know what programs are waiting for you on the demonstration cartridge. So, insert the cartridge into the microdrive (or, if you have several microdrives, into drive 1), and enter:

NEW
followed by:
RUN (and ENTER)

This will automatically load and run the first program on the cartridge. When you have finished watching this program, read on.

The catalogue

To find out what other programs are stored in the demonstration cartridge, enter the CATalogue statement:

• the name of the cartridge
• an alpabetical catalogue of the names of all the files stored in the cartridge
• the amount of memory left in the cartridge (in kilobytes)

Loading programs

The next thing to do is LOAD whichever program you would like to see next. So, first choose your program, then enter:

After a short pause the screen will display the OK message (though not the name of the program). You can now run the program.

Chapter 4 - Programs and the microdrive

Saving, verifying, loading and merging programs

In the ZX Spectrum introduction booklet you found out how to SAVE programs on a cassette tape. Saving programs in cartridges is just as easy. Here again is a program called Squares, much like the one in the introduction booklet:

To SAVE this on a cassette tape you would enter: SAVE"squares"
To SAVE it in the cartridge in drive 1, you would enter instead: SAVE*"m";1;"squares"
After about six seconds the border will flash, and the program will be saved. Try it and see. (The names of programs stored in a cartridge, like those of programs stored on a cassette tape, can be up to ten characters long.)

As you would expect, you can now check that the program has been saved by entering:

VERIFY*"m";1;"squares"
The screen will then display the OK message.

You can now LOAD the program squares by entering:
LOAD*"m";1;"squares" then ENTER

In short, as you have probably already realised, all the syntax used within an ordinary cassette interface applies also to the microdrive.

Erasing progams

Suppose you have just finished with the program squares. To erase it, enter: ERASE"m";1;"squares"
During the ERASE statement the border will flash.
If you BREAK while saving a program then you will have an unclosed file in the cartridge. You cannot LOAD an unclosed file, and an attempt to do so will give the report file not found. The ERASE statement can delete an unclosed file, but will take about thirty seconds to do so because the computer checks the cartridge several times to make sure that the file no end.

Formatting and naming blank cartridges

If you have bought a blank cartridge, before you can use it you must insert it into a drive and enter this:
FORMAT"m";1;"name"

Where name is whatever you wish to appear in the cartridge catalogue. It can be up to 10 characters. The computer takes avout thirty seconds to format a cartridge. During this time the border will first flash, then clear, then flash again, and finally display the OK message. What the computer is doing is identifying any areas that cannot be written to or read from and marking them to be avoided.

Formatting need never be repeated. Note, by the way, that when you format a cartridge, any information it contains will be erased. So, if you have bought sveral microdrives, you can FORMAT your spare demonstration cartridges and use them as blank cartridges.

Next type:
CAT 1 where 1 identifies the microdrive number.
In a few seconds, the television screen will display the cartridge's name and capacity. The capacity will vary from cartridge to cartridge, but it should never be less than 85 kB.

Setting up your own auto-run facility

Earlier, you used the auto-run facility on the demonstration cartridge. If you have a pgroam that you often use, you can set up your own auto-run facility, so as to avoid repeatedly having to type LOAD and RUN statements. These are the rules to follow:

• the program must be called run
• the cartridge must be in drive 1
• the facility must be used either immediately after switching on, or immediately after a NEW statement.

Now enter: NEW followed by: RUN then ENTER
Note, however, that the MERGE statement does not work with any program saved using the SAVE*...LINE... statement. (This is so as to protect such programs.) An attempt to MERGE will give the report 'Merge' error

Chapter 5 - Data, channels and streams

As, you know, a program is a set of operations which is executed when you type RUN. Data, on the other hand, is any collections of leters, numbers or symbols on which a program might operate. An example is the numbers 1 to 10 with their squares.
Data can be sent to, and come from, various parts of a computer system. Such parts are known as channels. The channels you can send data to are:

• your screen
• a ZX printer
• a microdrive file, to store it
• another ZX Spectrum computer, if both computers are on a network
• the RS232 interface and from there to a modem or printer

• the keyboard
• a microdrive file
• another ZX Spectrum, if both computers are on a network
• the RS232 interface, a modem or terminal

The routes along which the data flows to and from these channels are known as streams. In the spectrum computer system the number of these streams is fixed to sixteen. They are numbered from 0 to 15, and stream numbers are preceded by the sign #.
Four of these streams come already linked to channels:

Every statement that produces input or output uses one of these streams automatically. For example, the PRINT statement uses stream #2, and the LPRINT statement uses stream #3. So if you enter:
PRINT "This is a Spectrum Computer"
it is, in fact, shorthand for:
PRINT #2;"This is a Spectrum Computer"
try entering both and see.
You can, however, make any statement use a different stream by keying # followed by the new stream number. Try entering:
LPRINT#2;"This is a Spectrum Computer"
Instead of being printed by the ZX Printer, this line too appears on the screen.

But as well as using the established stream-channels, you can create some if your own. Streams #4 to #15 are free for this purpose; and there are various channel specifiers which enable you to indicate which peripheral you require. Some of these are:

Note that K, S and P are all established channels. They require you to use commas(,) as separators in OPEN# statements. But with other channels you can use either commas or semi-colons(;)

To create you own stream-channels you use the OPEN# statement. For example enter:
10 OPEN#4,"S"
You will have opened stream #4 and linked it to channel S. Now enter:
20 PRINT #4;"This is a Spectrum computer"
Again, the line will appear on the screen.
(It is not advisable to OPEN to streams 0, 1, or 2 as the results are unpredictable)

Data and the microdrive

Opening and naming a data file

When you store information in a cartridge you keep it in a file. You also give the file a name so that you can find it again later. The statement that opens and names a data file always takes the same form.

For example try entering:
OPEN#4;"m";1;"numbers"
Where #4 identifies the stream number.

This statement does two distinct jobs:

• it sets up a new channel: "m";1;"numbers"
• it attaches this new channel to stream #4

Entering data

Once you have opened a file you can enter data. Suppose that you want to store the numbers 1 to 10 with their squares. Enter and run this:

You might think that all the numbers have now been stored away in the cartridge. But in fact the computer does not automatically transfer anything to the cartridge until a certain amount has built up, which it transfers all at once. This is called buffering. A microdrive buffer is 512 bytes (or characters) long. To store in the cartridge the data you have entered you must CLOSE the file. Until this is done you will be unable to read back from the file.

Closing a file

Closing a file ensures that the file is safely stored in the cartridge. It also closes the channel (in this case "m";1;"numbers") and leaves the stream (in this case#4) with no channels attached. To CLOSE a file you need only CLOSE the appropiate stream. So enter:

The border will then flash to show that something is being store in the cartridge.
(Note that, like the OPEN statement, the CLOSE statement is followed automatically by #.)

You cannot by the way, CLOSE streams #0, #1, #2 or #3. If you try to do so, streams #0 and #1 will default to channel K; stream #2 will default to channel S; and stream #3 will default to channel P (see chapter 5)

Reading back from a file

To read back from the file "numbers", run this:
10 OPEN#4;"m";1;"numbers"
20 FOR b=1 TO 10
30 input #4;m;n
40 PRINT "The square of ";m;" is ";n
50 NEXT b
60 CLOSE #4

RUN

(Note at this point that because the file "numbers" already exits, the channel "m";1;"numbers" is opened for input, and trying to output to it would give an error.)

You can also use INKEY$ to read back from a ile (it always gives the next character in the file). Try this program:

This will finish with the End of file report.

Notes on PRINT and INPUT

Because the PRINT and INPUT statements are designed mainly for use with the screen and keyboard, you must take care when using them with files.

separators

The PRINT statement uses three forms of separator;

• the ; (semi-colon) prints nothing,
• the , (comma) takes you to the start of the next half-line,
• the ' (apostrophe) gives a new line (the ENTER code).

• print the items singly, e.g.
  10 PRINT #4;2
20 PRINT #4;3

• separate then with an apostrophe, e.g. 10 PRINT #4;2'3


You must also take care when using separators in an INPUT statement. As you know, INPUT can print to the bottom half of the screen anything that you can put in a PRINT statement. But when you INPUT from a file, the file is only open for reading. So, if you include anything that would be printed when using the screen, you will get the error report Writing to a 'read' file. This means that items in the INPUT statement should be separated with a semi-colon, e.g.

Be careful also when you INPUT a string containing " (quotes), because the INPUT will think that the " is the end of the string. The way round this is to replace, for example:

changing streams

PRINT statements may also contain information for several streams at a time. The following program will print "one" on the screen; "two" to a microdrive file called "digits" in microdrive 1; "three" to station 1 on a network (see Chapter 7); and "four" to the next line on the screen.

setting colours

After using a channel other than the screen, you may find that the PAPER and INK statements have no effect. To get round this, enter:

Reading the file catalogue

As you establish files in a cartridge they are automatically catalogued. So, when you want to find out what files a cartridge contains, you need only insert the cartridge into a microdrive and enter the CAtalogue statement. For example, enter:

The television screen will display:

• the cartridge name,
• the file names,
• the amount of memory left in the cartridge, (in Kb).

You can also send the output of CAT to a stream by entering:

This enables you to send the catalogue to a printer, or to a file, so that a program can use it.

Protecting a file

If you do not want a file name to appear on the catalogue, you can protect it by giving it a name beginning with the character whose CODEis 0. Enter this:

The file name will not appear. So, whenever you create a protected file, remember to make a note of its name somewhere, in case you forget it later!

Extending a file

Suppose you want to extend the file "numbers" to include the squares of numbers 1 to 20 instead of only 1 to 10. You cannot reopen a file for writing, so you will have to:

• make a new version with a different name;
• transfer the old file to the new version;
• add the extra data;
• delete the old file.

Now, to check that you have got two files, "numbers" and "numbers1", enter:
CAT 1
Next, to delete the old file, enter:
ERASE "m";1;"numbers"
To check that it has been deleted, enter:
CAT 1

The file name "numbers" will have disappeared from the catalogue, and your new file, "numbers 1" now contains the numbers from 1 to 20.

Chapter 7 - The local area network

Setting up a network

The local area network, or net, enables you and your friends to play computer games together, and to send each other programs and data. This means that only one of you need to type in a program. A net is especially useful, too, if only one of you has a Microdrive.

Using the lead supplied with each Interface you can link up as few as two and as many as sixty-four Spectrum computers.

Note, however, that you and your friends should not form a loop of computers: the computers at each end of the net should never be connected to each other. Each should be left with one net socket free.

NEVER SWITCH ON OR OFF A SPECTRUM WHICH IS ON A NET WHILE COMMUNICATION IS IN PROGRESS.
You may, however, have a switched off Spectrum on the net; and you may also switch on or off Spectrums which are on a net provided that communication is not in progress.

When you have set up a net, each computer (or station) should be given a different identification number. So, first decide with your friends what number each station it to have, and then each of you should enter:

Note, incidentally, that if there are only two computers on a net, both can use the same station number. And, since both computers, when switched on, become station 1 automatically, there is no need to use the FORMAT statement at all.

Programs and the network

Let us suppose that you have a friend called Jack and that both of your computers are on a net. Your station number is, let us say, 1, and Jack's is 2.

Jack will now have a copy of the program. Notice, though, that while the computer is waiting to SAVE or LOAD a program over the net, the border of the screen goes black until the program is sent. You computer will not send until Jack's is ready, and Jack's will wait until something is sent. Try entering your SAVE line before Jack enters his LOAD line, and vice versa.

SAVE is, in fact, the only statement that sends programs over the net. The LOAD, VERIFY and MERGE statements are all ways of receiving programs.

The net game in Appendix 1 is a good example of how to use programs with a network.

Data and the network

Suppose that you want to send Jack some data. The statement OPEN #4;"n";2 opens a channel to station 2 on the net ("n"), and attaches stream #4, to it, so that when you output along stream #4, your message will be put on the net with a note saying that it comes from you.

(Conversely, were you to enter INPUT #4;"n";2 your computer would wait for information addressed to you from Jack.)

You should now run your program, and Jack should edit lines 10 and 40 of the program to make them refer to station 1 not station 2. He should then enter:

You are now ready to start a conversation. But before you do so there are three things you should know:

• Your output along stream #4 is buffered: that is, it is not automatically put on the net until a certain amount of output has accumulated. So whenever you finish outputting you should CLOSE the stream. This will send the buffer even if it is not full. (The buffers are 255 bytes, or characters, long.)
• Your output is marked as coming specifically from you, so that if Jack is inputting or waiting for output from a different net channel, your message will be ignored. If your message has been ignored your screen will not display the OK message, and the border of the screen will go black, until Jack asks to receive the message.
• Though the INPUT statement simply waits for something to be sent, the INKEY$ statement can be used to read the net. It will return with the first byte of anything that either has been sent, or is waiting to be sent. (Otherwise it will return the empty string.) This is known as polling. (INKEY$, in fact, works the same way with the net as it does with the keyboard.)

Broadcasting

There is also a special net channel called broadcast whose channel specifier is "n";0. When you input from this channel you will pick up any message that is being broadcast. And when you output, you message can be read by anyone who is inputting from channel "n";0.

This could, for example, be very useful at school if every pupil in a class has a Spectrum computer, but only the teacher has a Microdrive.

Suppose the teacher wished to broadcast a program. First, the pupils should enter:

As you may have guessed, broadcast (unlike private messages) are sent at once, and do not wait for other computers to be ready to receive them.

Note, by the way, that when you send a broadcast, the computer does not let you know if anyone has received it.

Note also that INKEY$ will not poll the broadcast channel. Like INPUT, it will simply wait for something to be sent.

Chapter 8 - using the RS232 interface

Connecting peripherals tot he RS232 Interface

As you know, the Spectrum character set comprises both single symbols (letters, digits, etc.) and compound tokens (keywords, function names, etc.). All these characters can be sent and received by the RS232 Interface to and from any compatible serial device; for example, a printer, a modem or another RS232 Interface connected to a different kind of computer.

To connect any of these peripherals to the RS232, you should use a lead with a 9-way D-plug on one end and an appropriate plug for you peripheral on the other. You should insert the D-plug into the back of the RS232, as shown below. (For wiring details, see Appendix 4.)

Next, before you can use the RS232 you will need to adjust some of the settings on the peripheral. These may include:

• auto line feed, which should normally be switched to off. (The Spectrum outputs a carriage return and a line feed on a "t" channel but a carriage return only on a "b" channel. These t and b channels are explained below.)
• parity on/off, which should be set off.
• the number of bits, since the Spectrum puts out eight bits.
• the number of stop bits, since the Spectrum puts out one stop bit.
• the baud rate (i. e. the number of bits per second). The Spectrum can operate at all standard baud rates, i. e.: 50, 110, 300, 600, 1200, 2400, 4800, 9600 and 19,200.

You should set your peripheral to use the highest baud rate of which it is capable. (You will see later how to set the Spectrum to use the same baud rate.)

For an explanation of how to make these adjustments, consult the instruction book supplied with your peripheral.

The RS232 uses two different channels: the t channel and the b channel.

The t (or text) channel is normally used to send listings. Channel t has the following effect on the character set:

On INPUT and INKEY$ the t channel expects 7 bits characters, so it ignores the 8th bit if there is one.

To use the t channel, first you must tell the computer which baud rate to use. So enter:

Now to OPEN a stream to it, enter:

The border of the screen will flash and the listing will be sent to the peripheral. (Notice that LLIST is shorthand for LIST #3.) Now enter:

If your ZX Interface is connected to a terminal or an RS232 device capable of sending, then you can INPUT from the terminal or device. Enter this:

Now, whatever you type on the terminal or device will appear on your screen.

The b (or binary) channel sends the full 8 bit codes used by the Spectrum, and allows you to send control codes to printers etc.

With INPUT and INKEY$ the b channel expects 8 bit characters.

SAVE and LOAD will only work with the b channel.

If you are using modems to connect your computer with another Spectrum over a 'phone line; or if you are storing your programs on a different kind of computer which also has an RS232 Interface, you may well want to SAVE and LOAD over the RS232 Interface. To do this, enter:

Now, for example, enter: 10 REM figures
20 FOR n=1 TO 10
30 PRINT n,n*RND
40 NEXT n


followed by:

If this program is being send via modem, someone at the other end should enter:

The usual extensions are also possible, such as:

Many printers allow you to send instructions for such operations as double width printing. To send these you should use the b channel. However, with the b channel, the carriage return does not include a line feed. So you will have either to change the settings on your printer, or print the line feed code: 10.

For example, suppose that the control code for double width printing is 14. Enter:

(For the correct control codes to use, refer to your printer's instruction book.)

You can have both b and t channels at once. Try entering this:

This would give you a double width listing.

Chapter 9 - the MOVE statement

So far, you have only been able to move data from a program to a channel or vice versa. The MOVE statement, however, enables you to move data from one channel to another. For example, to move data from the keyboard to the screen, enter:

Anything you type on the keyboard will now appear on the screen. However, you will discover that when you press BREAK this only prints a space on the screen. To escape from this trap, press ENTER until the print position reaches the bottom of the screen. The, when the computer asks 'scroll?' you should press BREAK. (You should, by the way, avoid moving data from the keyboard to any other stream since you may be unable to BREAK out of such a mode.)

Using the MOVE statement you can also examine files stored in cartridges. For example, set up the file "Numbers" and then, to examine its contents, enter:

(Note that you need not OPEN or CLOSE the file yourself. MOVE does this.)

Similarly, to make a copy of the file "Numbers" enter:

Here, MOVE opens a stream for reading from the existing file ("Numbers") and another for writing to the new file ("Numbers 2"). Next, it reads the data in "Numbers" and writes it out in "Numbers 2". Then it closes both streams.

MOVE will work with stream numbers (such as #4), and with channel specifiers (such as "m";1;"Numbers"). Note, however, that the established streams, #1 to #3, may not be specified by the channel specifiers K, S or P.

If you have a second Microdrive, you can use the MOVE statement to make back-up copies of data in another cartridge. Enter:

(Note that MOVE only works with data files. If you want a back-up copy of a program, you must LOAD the program, and then SAVE it.)

It is sensible to make back-up copies of any data or programs you want to keep.

The MOVE statement can also send files to a printer. So if you have a ZX Printer, enter:

The Printer Server program

This program allows one Spectrum on a net to control an RS232 printer. The printer can then be used by all other computers on the net. This is useful, for example, if a group of people using Spectrums have only one high quality printer among them which they wish to share. The program also shows a powerful use of the MOVE statement.

The Printer Server computer must always be station 64, and must always make contact with station 62 (which is a contact establishing station). So the sender temporarily uses station 62, and sends it his real station number from which it then moves a files to the t channel. To set up a Printer Server station use this program:

(Line 40 sends a form feed.)

The program below is the one send by the sender. First, the sender's station is temporarily set to station 62. Then, the sender's real station number is sent. Next the sender's station sets itself back to its real number. Last, line 60 sends whatever data is to be printed (in this case, the listing).

Appendix 1 - The net game

There is a copy of this game on the demonstration cartridge supplied with the Microdrive. Its file name is "net game". The program gives a good example of how the net can be used. Parts of it might usefully be included in programs of your own.

The game

To play this game, you and your opponent must each think of a number between 1 and 100. The winner of the game is the one who guesses his opponent's number first. At each guess you make, your computer will tell you how close you are getting.

The program

The subroutine at line 500 decides who is user 1 and who is user 2. This is so that, when you exchange guesses, one of you uses the subroutine at line 1100, and the other uses the subroutine at line 1200 and thus user 1 sends first and user 2 receives first.

Your computer decides who is user 1 by sending your opponent's computer the message "1", and then listening. If it receives back a "1", this means that opponent's computer was switched on after yours. Your computer therefore sends a "2" to your opponent's computer, and makes itself user 1. (If, on the other hand, your computer receives back a "2", this means that your opponent sent the "1". Your computer will therefore make itself user 2.)

If both computers start at the same time they collide and it will be necessary to BREAK and start again.

The body of the program is involved with exchanging names, inputting the secret number (which is not sent) and then comparing guesses. First guesses are sent, and then the replies.

Lines 190 onwards detect a win, signal it appropriately, and then offer another game.

Appendix 2 - system variables

In addition to the system variables given in Chapter 25 of the Spectrum BASIC programming manual, the Microdrive, local area network and RS232 software use the system variables below.

Notes   Address Name    Contents
X1      23734   FLAGS3  Flags
X2      23735   VECTOR  Address used to extend the BASIC interpreter
X10     23737   SBRT    ROM paging subroutine
2       23747   BAUD    Two byte number determining the baud rate
                        calculated as follows:
                        BAUD=(3500000 / (26 * baud rate)) - 2
1       23749   NTSTAT  Own network station number
1       23750   IOBORD  Border colour used during I/O. You can poke
                        any colour you want.
N2      23751   SER_FL  2 byte workspace used by RS232
N2      23753   SECTOR  2 byte workspace used by Microdrive
N2      23755   CHADD_  Temporary store for CH_ADD
1       23757   NTRESP  Store for network response code
1       23758   NTDEST  Beginning of network buffer contains
                        destination station number 0-64
1       23759   NTSRCE  Source station number
X2      23760   NTNUMB  Network block number 0-65535
N1      23762   NTTYPE  Header type code
X1      23763   NTLEN   Data block length 0-255
N1      23764   NTDCS   Data block checksum
N1      23765   NTHCS   Header block checksum
N2      23766   D_STR1  Start of 8 byte file specifier
                        2 byte drive number 1-8
N1      23768   S_STR1  Stream number 1-15
N1      23769   L_STR1  Device type... "m", "n", "t" or "b"
N2      23770   N_STR1  Length of file name
N2      23772   D_STR2  Second 8 byte file specifier
                        used by MOVE and LOAD commands
N1      23782   HD_00   Start of workspace for SAVE, LOAD, VERIFY and
                        MERGE data type code
N2      23783   HD_0B   Length of data 0-66535
N2      23785   HD_0D   Start of data 0-65535
N2      23787   HD_0F   Program length 0-66535
N2      23789   HD_11   Line number
1       23791   COPIES  Number of copies made by SAVE
        23792   Start of Microdrive MAPs or CHANS

Warnings

1. Opening a stream to the Microdrive or net requires a certain amount of free memory with which to create a channel. A Microdrive channel is 595 bytes, and a net channel is 276 bytes. These channels will be created either by OPEN #, MOVE or by SAVE / LOAD / VERIFY / MERGE. This means that an existing program with insufficient room below RAMTOP will give the report 'Out of memory' to any of these operations.
2. Another effect of the creation of these buffers is to move machine code stored in a REM statement. This may create problems. So always put machine code programs above RAMTOP.
3. It is inadvisable to BREAK during a Microdrive write operation (one during which the border is flashing), since you may end up with an unclosed file. ERASE will remove unclosed files, but will take about thirty seconds to do so, as the computer checks the cartridge several times to make sure that the file has no end.

Appendix 3 - Microdrive channel

Every time a file is opened an area called a CHANNEL is created in the area designated CHANS in the BASIC programming manual. This area is usually addressed by the IX register in the software. The channel has a length of 596 bytes, and contains the 512 byte buffer.

The contents of the channel are as follows:

0               Address 8
2               Address 8
4               'M'
5               Address of output subroutine in ROM
7               Address of input routine in ROM
9               Address 595
11      CHBYTE  Current byte counter indicates the next byte to be
                added or removed from the data area in the range 0-512
                inclusive
13      CHREC   Record number. Indicates the position of the record in
                a file range 0-255
14      CHNAME  10 byte filename with trailing spaces
24      CHFLAG  Flag byte       bit 0    set...open for write
                                         clear open for read
                                bits 1-7 unused
25      CHDRIV  Drive number 0-7
26      CHMAP   Address of the MAP for this Microdrive
28      CHMAP   12 bytes of header preamble... marks the start of the
                header workspace
40      HDFLAG  Flag byte       bit 0    set
                                bits 1-7 unused
41      HDNUMB  Sector number in range 0-255
42              Unused
44      HDNAME  Cartridge name and trailing spaces
54      HDCHK   Header checksum
55              12 Bytes of data block preamble... marks the start of
                the data workspace
67      RECFLG  Flag byte bit 0 = 0
                          bit 2 = not a PRINT file
                          bit 3-7 unused
68      RECNUM  Number of this record in the range 0-255
69      RECLEN  Number of bytes of data in this record 0-512
71      RECNAM  Filename with trailing spaces
81      DESCHK  Checksum of the preceding 14 bytes
82      CHDATA  512 bytes of data
594     DCHK    Checksum of the preceding 512 bytes

Map

For every Microdrive containing an opened file there is an area called MAP created in the area called "Microdrive maps" in the BASIC Programming manual. The MAP contains 32 bytes. Each bit corresponds to a sector on the corresponding Microdrive. If that sector contains data or if it is unusable then the bit is set. The bits are numbered as follows: bit 0 byte 0 = sector 0, bit 1 byte 0 = sector 1, bit 0 byte 1 = sector 8, and so on.

Network channel

When a stream is opened to the network, a channel is created in the area designated CHANS in the BASIC Programming manual. This area is usually addressed by the IX register in the software. The channel has a length of 276 bytes, and contains the 255 bytes buffer.

The contents of the channel are described as follows:

0               Address 8
2               Address 8
4               "N"
5               Address of output subroutine in ROM
7               Address of input subroutine in ROM
9               Address 276
11      NCIRIS  The destination station number
12      NCSELF  The Spectrum's station number
13      NCNUMB  The block number
15      NCTYPE  The packet type code... 0 data, 1 EOF
16      NCOBL   Number of bytes in the data block
17      NCDCS   The data checksum
18      NCHCS   The header checksum
19      NCCUR   The position of the last character taken from the
                buffer
20      NCIBL   The number of bytes in the input buffer
21      NCB     A 255 byte data buffer

Appendix 4 - RS232 connections

/----------------------\
\ 5 o   o   o   o   o 1/
 \  9 o   o   o   o 6 /
  \------------------/

The RS232 socket is wired as follows:

An RS232 cable is available from Sinclair Research, which connects the 9 way D-socket to a 25 way D-plug (25 way D-sockets are common on RS232 peripherals). For details of how to obtain this cable, see the software and peripherals catalogue included with the ZX Interface 1. This cable is wired as follows:

Appendix 5 - Reports

Now that you have attached a ZX Interface 1 to your computer, your programs may produce reports which are not described in Appendix B of the BASIC programming manual. Such reports will be followed by the line number and the statement number at which the program stopped.

These new reports are explained (in alphabetical order) below.

You have tried to LOAD a code block that is larger than the destination area specified by your LOAD statement.

You have tried to write data to a Microdrive containing a protected cartridge (i. e. one with the plastic tab on the side removed).

This means that either you have tried to LOAD from a file which does not exist, or part of the file cannot be found. (This would either be because the file has not been closed, or because the file has been damaged by the power being switched on or off while the cartridge was in a Microdrive.)

A device has been specified other than s, p, k, m, n, t or b. The same report can be produced if a semi-colon, rather than a comma, is used with one of the channels s, p or k.

A Microdrive number has been specified outside the range 1 to 8.

A file name has been specified as an empty string or a string with more than ten characters.

A network station has been specified outside the range 0 to 6 (or outside the range 1 to 64 for FORMAT statements).

A stream has been specified outside the range 0 to 15.

You have tried to MERGE data or code. You can only MERGE programs. This report will also appear if you have tried to MERGE a program saved by the SAVE... LINE... statement.

You have tried to write data to a cartridge containing no free space. You should therefore run your program or command again, with a cartridge that does contain free space. This can be done by erasing old files from the present cartridge. A file opened for writing on the full cartridge cannot be closed. It should be erased. This will, however, take about thirty seconds because the computer checks the cartridge several times to make sure that the file has no end.

You have either tried to use a Microdrive which is not attached to your computer, or a Microdrive which does not contain a cartridge, or a Microdrive containing an unformatted cartridge.

The baud rate has not been specified.

The Microdrive number has not been specified.

The file name has not been specified.

The network station number has not been specified.

You have tried to execute a line beyond any existing line. This report will appear if a GO TO instruction is followed by a number beyond any existing line. It will also appear if RUN is typed without a program.

You have tried to input from a file which does not yet exist, or which has already been opened for input.

You have tried to OPEN to a stream which has already been opened to a new channel (m, n, t or b). The stream can only be opened if it is first closed.

A saved file does not agree with the program, data or code currently in the computer.

You have tried to output data to an existing file. The existing file should be erased if it is not needed. Otherwise, a new file should be used.

You have tried to INPUT or MOVE a saved file or to LOAD, VERIFY or MERGE a PRINT type of file, or to LOAD a CODE or DATA files as a program (or vice versa).
If you are using INPUT then you should be using LOAD. If you are using LOAD then either you should use the CODE to DATA options or you should use INPUT.

Appendix 6 - the extended BASIC

The ZX Interface 1 extends the BASIC already in the Spectrum. The extensions and additions are summarised below.

Streams are specified as #n where n is a number in the range 1-15. Streams 1, 2 and 3 are usually used by BASIC. The # character is part of the keyword for the OPEN # and CLOSE # statements.

There are seven types of channel in the extended BASIC; the keyboard (k), the screen (s), the ZX Printer (p), the text RS232 Interface (t), the binary RS232 Interface (b), the network (n) and the Microdrive (m).

Each channel type is specified by its letter which may be upper case or lower case. The network and the Microdrive require additional information to specify the channel completely.

A network channel requires a station number, so a network channel is specified as "n";x where x is a station number in the range 0-64.

A Microdrive channel requires a Microdrive number and a file name, so a Microdrive channel is specified as "m";y;"name" where y is the Microdrive number in the range 1-8 and "name" is a string of between 1 and 10 characters.