How's about something like this:


PARALLEL

	A1000 provides a male D-25 connector (DB25P), A500 and A2000 provide
female D-25 connectors (DB25S).

Signal		    A500 Pin	    A1000 Pin	    A2000 Pin

/STROBE			1		1		1
D0			2		2		2
D1			3		3		3
D2			4		4		4
D3			5		5		5
D4			6		6		6
D5			7		7		7
D6			8		8		8
D7			9		9		9
/ACK			10		10		10
BUSY			11		11		11
POUT			12		12		12
SEL			13		13		13
+5V [1]			14		23		14
/RESET			16		25		16
GND			17-25		14-22		17-25

[1] +5V on the A500/A2000 is resistively current limited to about 10mA to
    protect the system against some standard printer cables, which may ground 
    this line.


SERIAL

	A1000 provides a female D-25 connector (DB25S), A500 and A2000
provide a male D-25 connector (DB25P).

Signal		    A500 Pin	    A1000 Pin	    A2000 Pin [2]

Shield GND		1		1		1
TxD			2		2		2
RxD			3		3		3
RTS			4		4		4
CTS			5		5		5
DSR			6		6		6
Signal GND		7		7		7
CD			8		8		8
+12V [1]		9		23		9
-12V [1]		10		N/A		10
Audio OUT		11		15		11
Audio IN		18		16		18
DTR			20		20		20
RI			22		N/A		22
-5V [1]			N/A		14		N/A
Buffered E		N/A		17		N/A
/INT2			N/A		18		N/A
+5V [2]			N/A		21		N/A
/C2			N/A		24		N/A
/RESET			N/A		25		N/A

[1] +/- 12V on the A500 is resistively currently limited to about 10mA for
    protection.  +/- 12V on the A2000 is diode protected and current limited
    to about 200mA.  +/- 5V and +12V are not physically limited in any way on
    the A1000; care must be used in hooking up external cables, as the wrong
    connection could damage the A1000 internal circuitry.

[2] A1000 signals not present on the A2000 serial connector are available on
    a 26 pin header internally.