There are many different ways in which you can configure the SCPC88; they are selected by jumpering the links on the board. It is assumed in the following description that you are looking at the component side of the board, with the 64-way bus connector to the right.
Note:
+ indicates the standard link option, as supplied.
* indicates a signal is active low.
Link positions
o A LK1A SCPC88 reset switch may be connected across this link o B LK1B SCPC88 reset from STEbus SYSRST* o + C LK1C SYSRST* from SCPC88 o
o A LK2A The speaker connects to +5V and speaker output. o (the normal connection) B LK2B The speaker connects to OV and speaker output. o
The speaker is usually connected between 5V and the open-collector output of TR2 (i.e. across LK2A).
LK4 LK3 o o o o LK3 made only: 40 x 25 colour display only. LK4 made only: 80 x 25 colour display only. + LK3 and 4 unmade: mono/colour display. LK3 and 4 made; no video. (EGA board not fitted).
There is no link area 5. It has been renamed PL5.
LK8 o o o o LK6 o o LK9 o o LK7 o o + LK6 IC27 pin 27 is A14 (32/64K EPROM 27256/27512) + LK7 IC28 pin 1 is A15 (64K EPROM 27512) + LK8 1C28 pin 27 is A14 (32/64k EPROM 27256/27512) + LK0 IC27 pin 1 is A15 (64K EPROM 27512)
Links 6-9 should be left unmade for 8k or 16k EPROMs (type 2764 and 27128 respectively).