Jupiter Ace - i/o Ports
	-----------------------

	2005-11-14	Kio
	2008-06-03	Kio

There is only one io port: $FE. 
Only address bit A0 is decoded.

The beeper is set by out($FE) and reset by in($FE).

out(FE) data bit D3 sets the MIC-OUT line.
in(FE) data bit 5 reads the EAR-IN line.

Reading the keyboard:
This is identical to the ZX Spectrum design.
The 8 bits of the high byte of the io address select the row to scan. The row bits are active low.
Then D0 to D4 return the state of the 5 keys of this matrix row. The returned key bits are active low.

The high byte of the io address can be set with register A for in A,(NN) or with register B for in REG,(C):

1)	ld	a,$FE		; e.g. keyboard row 0
	in	a,($FE)		; read keys from row 0
	and a,01Fh      ; mask the unset bits
	
2)	ld	bc,$FEFE	; e.g. keyboard row 0
	in	a,(c)		; read keys from row 0
	and a,01Fh      ; mask the unset bits
	
In the ACE Rom, the address popped off the data stack is 16 bit, so with 16 BASE C! 0FEFE IN . will display the key depressions.
The keyboard layout is nearly identical to the ZX Spectrum, only the bottom rows are shifted and cursor up and down are swapped.

                Bit 0 = 0   Bit 1 = 0   Bit 2 = 0   Bit 3 = 0   Bit 4 = 0
Bit 0 (0xFE)    Shift       SymbolShift Z           X           C
Bit 1 (0xFD)    A           S           D           F           G
Bit 2 (0xFB)    Q           W           E           R           T
Bit 3 (0xF7)    1           2           3           4           5
Bit 4 (0xEF)    0           9           8           7           6
Bit 5 (0xDF)    P           O           I           U           Y
Bit 6 (0xBF)    Enter       L           K           J           H
Bit 7 (0x7F)    Space       M           N           B           V