Date   : Mon, 10 Jul 2006 13:15:47
From   : Rob <robert@...>
Subject: Re: RE EPSON LX-400

At 11:19 10/07/2006, drage@... wrote:
>TO connect it I used a parallel port 25pin d connector to ribbon connector as
>found on IBM PC motherboards to connect the older PCs case ports to the board.

I suspect that's where the problem lies ..  PC printer internal
connectors did vary slightly between makes and brands.  They also
expect to provide more signals that the Beeb uses, and less ground
signals, so you're probably connecting the printer status signals
down to ground.

Check your cable very carefully - if you are converting to a PC type
port, so as to use a PC printer cable, you will only need something like this
:

BBC PRINTER PORT                25 pin D-Sub Connector
1  strobe  --------------------- 1 strobe
3  d0 -------------------------- 2 d0
5  d1 -------------------------- 3 d1
7  d2 -------------------------- 4 d2
9  d3 -------------------------- 5 d3
11 d4 -------------------------- 6 d4
13 d5 -------------------------- 7 d5
15 d6 -------------------------- 8 d6
17 d7 -------------------------- 9 d7
19 ACK ------------------------ 10 ACK
21 n/c                   11 busy
23 n/c                           12 paper end
25 n/c                           13 select
                                  14 autofeed
                                  15 error
                                  16 initialise
                                  17 select in
all odd pins 2-24  ground ----- all pins 18-25 ground
26 n/c

(numbered
2 4  6                           1  2  3
1 3  5 ..etc                      14 15 16 ..etc )

As the beeb provides more ground pins (basically, every alternate
wire on the ribbon) than is expected from a PC compatible port, you
are going to be shorting out signals on the printer, causing the
lockup. Select In is probably the main culpret here!

Assuming your cable actually connects pin 1 on the IDC to pin 1 on
the DB25, pin 3 on the IDC to pin 2 on the DB25, etc., then if you
can manage to cut wires 2,4,6,8,10 on the ribbon then you might get
away with your adapter..

I'd definitely recommend making up a new cable direct from the beeb
to the printer - there's no fiddling needed in that case as it's a
straight through crimp all 26 wires from an IDC header to the start
of an IDC centronics connector.

refs:
BBC Micro User guide p503
http://www.interfacebus.com/Design_Connector_Parallel_PC_Port.html
http://www.interfacebus.com/Design_Centronics_Connector_PinOuts.html


Rob.