Hi Geoff,

A bit map of Einey mother board can be downloaded from the web site.

http://mysite.wanadoo-members.co.uk/retrocomputer/download.htm
http://mysite.wanadoo-
members.co.uk/retrocomputer/download/mb_wiring.zip

Thanks for the correction.
I was using the wrong pair of glasses miss read &47 for &4F in the
Einey Mags.
Unfortunately making a change made no difference.

I don't know if my theory is right but I tried this test.

I ran this BBCBASIC prog on Einey for the user port without anything
connected to it.

10 PUT &33,&4F
20 N=GET(&32)
30 PRINT N
40 GOTO 20

The value of N variable 253 streamed down the screen probably a
default value.

According to the Z80 PIO manual if a steady high is applied to STB
pin 11 without a negative pulse the data from the port should not be
accessed.

To test I crossed pin 11 STB with pin 1 5v. The streaming didn't stop.

I think the Z80 PIO handshake for mode 1 and 2 on Einey has been hard
wired out for normal access just leaving line input and output. STB &
RDY for the port a must be available for Einey's printer driver. So
it might be available with some other configuaring.

This extract from the Tatung Einstein Hardware Manual
might hold the answere.

Parallel Input/Output (Printer and User I/0)

The PIO has two 8 bit parallel ports which can be used as
either inputs or outputs under software control. Port A is
dedicated as a printer output by the MOS at power-on, and
this port has a monostable (1053b) which provides a (lus)
pulse triggered by the Ready (ARDY;I063 pin 18) line of the
PTO port A and is fed to the STROBE output (M001, pin 1).
This pulse is needed to comply with the Centronics printer
-interface timing. As well as the eight data-line outputs
(1063 pins 7,8,9,10,12,13,14,15) which are fed direct to the
printer connector (M001 pins 3,5,7,9,11,13,15,17
respectively). there are three "handshake" input lines from
the printer connector BUSY, PAPER EMPTY, ERROR (M001 pins
21,23,28) which are connected to the tri-state buffer 1036
(pins 15,13,11) to allow printer error conditions to be
detected. The even-numbered pins of the printer connector
(M001) are connected to OV.

The data-lines from port B (1063 pins
27,28,29,30,31,32,33,34) are connected to the user 1/0
connector (M002, pins. 2,4,6,8,10,12,14,16) and the Ready
(BRDY; I063 pin 2) is connected to M002 pin 5. Strobe lines
from each connector (M001, pin 19 and M002 pin 11) are
connected to pull- up resistors R057 and R058 as well as the
strobe inputs of the P10 (ASB,BSTB; 1063 pins 16,17
respectively)


Try to make sense of it later.

Thanks for your help.

Regards Chris Coxall