Currah Microspeech for ZX Spectrum

Currah Microspeech (Currah µSpeech)

Currah µSpeech interface Manufacturer: Currah Computer Components Ltd.
Graythrop Industrial Estate, Hartlepool TS25 2DF
Released: 1983
Original retail price: £29.95

Currah was acquired by dk'tronics in 1985. dk'tronics continued to manufacture the MicroSpeech unit, and many of their software titles supported it.

Blurb

Micro Speech is easy to use – simply plug into your Spectrum and TV and enjoy a new dimension; instant voicing of all the keys, infinitive vocabulary at your command, intonation to add character to speech, exciting new range of sound and speech games. Micro Speech talks through your TV's loudspeaker, ensuring top quality sound. Unlimited vocabulary means that Micro Speech can say anything. There is nothing it cannot say!

The unit uses an allophone system, which means that like you and I it doesn't care about the writing or spelling of the words, but simply speaks by concatenating speech sounds (allophones). To this purpose the string variable s$ has been reserved.

The unit contains a ULA which works on a WRITE command from the microprocessor, a ROM containing the keyword speech patterns and SP0256-AL2 speech processor. It also contains a clock for clear speech and an audio modulator to transfer the sound to the TV lead. The sound can be adjusted by using a screwdriver on the screw showing at the top right hand side of the unit.

The µSpeech allocates itself the top 256 bytes of memory at switch-on and moves down the USR graphics and RAMTOP. More can be allocated to that buffer by the use of CLEAR.

It plugs into the TV and the Mic socket and provides both, video and audio, to it's own TV output.

Draw backs

Audio is not output separately. So to use it, you must connect the Specci to your telly via aerial TV socket.

this is not completely true: the audio signal was also available on the 3.5mm plug. You could plug this into any audio amplifier like your HiFi equipment.

For cost reasons, the unit did not provide a system bus connector on it's rear side. Sadly, most joystick interface manufacturers took the same approach, meaning that you could not have a joystick and the MicroSpeech unit plugged in at the same time. But Currah could sell another item: the Currah µSlot. >:-)

The unit allocated itself the top 256 bytes of memory at switch-on and moved down the USR graphics and RAMTOP. This made it incompatible with some programmes, particularly games, which used that space for machine code.

Some games will not run while this unit is attached, notably the RoboCop arcade game port.

Odd bits (from Wikipedia)

By default, the unit spoke every key-press the user made, even the direction keys which came out as "CURSOR". This could be controlled by a reserved variable KEYS. Typing LET KEYS=0 would turn this feature off.

Booty (Firebird Software Ltd) detected the presence of a MicroSpeech unit and presented the user with a completely different game to that which would be played if the MicroSpeech unit was not present.

Programming speech (from Wikipedia)

Specific words and phrases could be spoken by assigning a value to the reserved string variable S$. This was interpreted letter-by-letter unless brackets were used to denote other allophones. A simple example would be "(dth)is", (dth) representing the voiced dental fricative /ð/. Sixty-three allophones were provided. Rudimentary pitch modulation could be achieved by altering the case of the letters—upper case letters being pronounced at a slightly higher pitch.

A more complex example:

5 REM OKAY WISEGUY THIS IS IT
10 LET a$=" (oo)K (AA)"
20 LET b$="w(ii)z (ggg) (ii),"
30 LET c$=" (dth)is iz it"
40 LET S$=a$+b$+c$

Technical details

The unit contained a ULA which worked on a WRITE command from the microprocessor, a ROM containing the keyword speech patterns, and an SP0256-AL2 speech processor. It also contained a clock for clear speech and an audio modulator to transfer the sound to the TV lead. A small adjustment screw was provided, to allow fine tuning of the audio output.

Supported Games

Very likely to be incomplete.

Title                Publisher
3-D Monster Chase       Romik Software
3D Lunattack            Hewson Consultants Ltd
3D Monster Maze         Romik
All or Nothing          Abbex Electronics Ltd
Arrow of Death 1        Digital Fantasia
Arrow of Death 2        Digital Fantasia
Auf Wiedersehen Pet     Tynesoft
Bingo                   Tynesoft
Blade Alley             PSS
Blastermind!            Martech Games Ltd
Blasteroids             Martech
Bongo                   Anirog Software
Booty                   Firebird Software Ltd
Cagara                  Players Software
Colour Clash            Romik Software
Connect 4               John Westhead
Crazy Golf              Mr. Micro Ltd
Currah MicroSpeech                  Currah Computer Components Ltd
Currah MicroSpeech Demonstration    Aardvark Software of Hartlepool
Currah MicroSpeech Software         Cecomsa
Electro-Man in Revenge of the Bugs  Sinclair User
Firebirds               Lyversoft
Fruit Snapper           LiveWire Software
Giant's Revenge         Thor Computer Software
Grand Prix Driver       Britannia Software Ltd
Gremlins                Thor Computer Software
Harlequin               Mr. Micro Ltd
Hunchback               Ocean Software Ltd
Insult Generator        Greg Fox
Jack and the Beanstalk  Thor Computer Software
Jack and the Beanstalk  Your Computer
Learn with Ted          Playground Software
Lunar Jetman            Ultimate Play The Game
Lunar Rescue            Lyversoft
Max Headroom            Quicksilva Ltd
Maze of Terror          Kevin Hillyer
Maziacs                 DK'Tronics Ltd   (i don't hear any speech [kio])
Mega Fruit              Thor Computer Software
Mined-Out               Quicksilva Ltd
Moon Alert              Ocean Software Ltd
Mr. Wimpy               Ocean Software Ltd
Mystic Tower            Aardvark Software of Hartlepool
Night Stalker           Thor Computer Software
Pi-Balled               Automata UK Ltd
Pogo                    Ocean Software Ltd
Pontoon                 Oxford Computer Publishing
Powerhouse              Your Computer
Psi-Spy                 Postern Ltd
Punchy                  Mr. Micro Ltd
Rainy Day               CCS
Rockfall                Crash
Rockfall II             Crash
Roulette                Oxford Computer Publishing
Sexy Black Jack         Load 'n' Run [IT]
Shark Attack            Romik Software
Skelby - The Schizophrenic Droid        QBIT
Spectrum Voice Chess    Artic Computing Ltd
Spiders Web             Thor Computer Software
Sport of Kings          Mastertronic Added Dimension
Spyship SOS             Dynamic Software
Starbike                The Edge
Steve Davis Snooker     CDS Microsystems
Terrahawks              CRL Group PLC
The Birds and the Bees  Bug-Byte Software Ltd
The Blob                16/48 Tape Magazine
The Covenant            PSS
The Evil Dead           Palace Software
The Golden Baton        Digital Fantasia
The Island              Crystal Computing
The Time Machine        Digital Fantasia
The War of the Worlds   CRL Group PLC
Timebomb                CDS Microsystems
Titanic                 R&R Software Ltd
Twin Kingdom Valley     Bug-Byte Software Ltd
Voice Chess             Artic
Word Generator          ZX Computing
Xavior                  PSS
Zepherus                National Software Library
Zig Zag                 DK'Tronics Ltd

Technical Details on Currah Hardware

Loosely based on nocash / problempakutt.de, by my own research and by Thomas Busse:

Hardware

The hardware must be 'enabled' to be accessible. Any access to anything with address $0038 toggles the 'enable' state of the interface. This means: memory read, write, input, output and program execution. It just doesn't matter. The last condition, execution, is used to enable the interface and it's rom when the regular system timer interrupt restarts here, to switch in the interface rom, execute some code therein and finally just jump to this address again to switch the interface off and resume execution of the normal interrupt code in the ZX Spectrum rom. There are no further BIOS hooks; initialization upon reset is also done from inside of the hooked IRQ handler.

Normally a RST7 or a memory read at address $0038 is used to toggle the rom. Rockfall II (but not Rockfall) interestingly used IN $0038 to toggle the rom to detect the presence of the interface. I wouldn't recomment to use I/O for that because of the many '0' bits which will activate lots of other hardware! I actually learned something about the IN opcode from this code snippet which i probably just had forgotten some years ago…

When the interface is 'enabled', then the rom and the SP0256 speech processor are visible and can be read or accessed. The interface uses memory mapped i/o to access the SP0256 speech processor.

The address space of the interface is $0000 to $3FFF, but only bits A12 and A13 are actually used. So there are these 4 addresses:

$0XXX  r: access the rom, w: void
$1XXX  access the SP0256
$2XXX  unknown
$3XXX  w: set the intonation flag; r: unknown

The ZX Spectrum rom is fully disabled (all 16 kB) while the interface is enabled.

The µSpeech rom is only 2 kB in size and it is visible at address $0000 and mirrored at address $0800.

Writing to address $1XXX writes the lower 6 bits as a command into the SP0256. The AL2 rom has only 64 allophone entry points and the upper 2 bits are hard-wired to 0.

Reading from address $1XXX reads the busy bit (Load Request /LRQ) in D0: 1=Buffer full, 0=Ready to receive data. The upper bits contain garbage and are not always pulled high as might be expected. Also the busy bit occassionally seems to return 'busy' even when the interface is idle. (see video on Thomas Busse's page.) /LRQ is set when a command is written to the command register and cleared when the SP0256 state machine reads it. So, as soon as it becomes 0, the next command can be written to the SP0256. The SBY pin (indicating when all data is finished) is probably not connected. (to be verified. Seen by the timing of the busy bit it may well be the SBY pin instead.)

Data can be written to SP0256 when status bit 0 is low. Otherwise the old command in the command register is overwritten. The last allophone should be followed by a pause (eg. 00h=Pause10ms), because the SP0256 cannot stop but continues to generate noise with the last filter setting until a new command is written to the command register. It does not repeat the whole command.

Writing to address $3XXX sets the 'intonation': Address bit A0 set's intonation to low frequency (A0=0: ~3MHz clock / ~10kHz samples) or high frequency (A0=1: approx. 7% higher). The shift in frequency is soft and takes around 0.05 to 0.5 seconds, the timing seems to vary (Thomas Busse). The data value written is not used.

The intonation bit is a special feature of the Currah hardware, not of the SP0256 speech chip itself. It modifies the CLK passed to the SP0256. So, aside from the frequency, this also alters the durations of all allophones and pauses.

Currah µSpeech BIOS/BASIC extension

Unlike most or all other speech devices, the Currah hardware includes a BIOS extension. Currah related BASIC commands are:

LET keys=0           ;disable spoken keystrokes (recommended for LOAD/SAVE)
LET keys=1           ;enable spoken keystrokes (default)
LET s$="he(ll)(oo)"  ;say hello (normal lowercase)
LET s$="hE(ll)(oO)"  ;say hello (with raised intonation on "e" and "(oo)")
PAUSE 1              ;wait for Vblank IRQ (where s$ is processed)
CLEAR n              ;change RAMTOP (speech buffer is between RAMTOP and UDG)
IF PEEK(65364)=81    ;buffer pointer LSB, [FF54h]=51h=buffer_empty (on 48K)
IF s$(TO 1)="*"      ;check if s$ was processed (copied to speech buffer)
IF s$(TO 1)="?"      ;check if s$ was rejected (contained invalid characters)
IF s$(TO 1)=other    ;check if s$ was not yet processed (or buffer full)

On power up, the Currah BIOS allocates 256 bytes between RAMTOP and UDG, containing a 6-byte "header", and a 250-byte buffer; which contains allophone numbers (and intonation flag in bit6), in the format as written to address to 1000h (ie. not in ASCII format as used in the BASIC s$ variable). On the Spectrum this region is at FFxxh (on Spectrum 16K it's at 7Fxxh):

FF57h - Flag byte
FF56h - Spare (unused general purpose byte; NOT reserved for anything)
FF55h - Hi byte of buffer pointer ;ntains FF51h when empty
FF54h - Lo byte of buffer pointer ;/
FF53h - Spare (unused general purpose byte; NOT reserved for anything)
FF52h - Spare (unused general purpose byte; NOT reserved for anything)
FF51h..FE58h - Speech buffer (default size=250) [FF51h]=next allophone

In BASIC, the spoken keystrokes and s$ strings are good for a first "oh it does really speak" impression, although after soon, the keystroke feature may become annoying, and the automatic modification of the first character in s$ may cause compatibility problems with various BASIC programs that do use s$ for other purposes.

Moreover, allocating 256 bytes between RAMTOP and UDG may cause problems with many machine code programs. And, hooking the IRQ handler changes Vblank handling timings which may also cause problems with a few programs.

Name	Letzte Änderung	Länge
Current Selling Prices/	2019-08-20 05:24	10
Games for Currah µSpeech/	2019-08-22 19:20	34
Technical Information/	2020-08-27 14:08	18
XL/	2019-08-20 05:24	1
All the stuff.jpg size: 430 × 378	2005-11-02 12:32	72191
Box - front-2.JPG size: 321 × 400	2008-07-22 13:30	31103
Box - front.jpg size: 400 × 300	2006-02-07 12:10	32318
Box - rear side.jpg size: 400 × 300	2006-02-07 12:11	31424
Box, torn, front side.jpg size: 640 × 480	2015-04-21 16:06	66739
Box, torn, rear side.jpg size: 640 × 480	2015-04-21 16:06	66274
Compiling Words (1983, Currah).z80	1996-12-24 22:32	5355
Currah µSpeech - Hot Spot (redclash).jpg size: 1207 × 905	2017-10-29 10:10	184542
Currah µSpeech - open (redclash).jpg size: 1207 × 905	2017-10-29 10:09	268971
Currah µSpeech - PCB rear side (redclash).jpg size: 723 × 542	2017-10-29 10:47	99854
Currah µSpeech.jpg size: 400 × 318	2005-11-02 12:57	37603
CurrahMicroSpeech Ad#2.jpg size: 800 × 1166	2015-04-21 16:06	195126
CurrahMicroSpeech Ad#3.jpg size: 800 × 1148	2015-04-21 16:06	192966
CurrahMicroSpeech Ad#4.jpg size: 945 × 1335	2015-04-21 16:06	242369
CurrahMicroSpeech-1.jpg size: 615 × 873	2015-04-21 16:07	110115
CurrahMicroSpeech.jpg size: 593 × 567	2015-04-21 16:06	57784
Manual.html	2005-12-01 10:54	31886
Manual.pdf	2017-10-28 14:53	137791
Manual.txt	2005-12-01 10:55	26541
Setup with Specci.jpg size: 600 × 450	2007-01-21 20:14	65326
SP0256-AL2 cc-by-sa ZyMOS.png size: 694 × 321	2013-10-04 12:35	287761
Tape - side 1.tzx	2001-12-06 18:55	20032
Tape - side 2.tzx	2001-12-06 18:53	15004
Hardware feature [WoS]		112
problemkaputt.de - hardware ports doku		113
Thomas Busse – obscuretronics		113
ZX Spectrum with Currah microspeech for sale - YouTube		104

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