Connector Pins; P1 - Ram Size Selector; P2 - Dma Requests; P3 - Flash Bootload Selector - David Griffith P112 Assembly And Operation Manual

9

Connector Pins

The pin assignments of the various connectors are tabulated below. All are 0.1"
pitch headers.
9.1 P1 — RAM Size Selector
Pin Assigment
1 Address decoder input
2 A17 (128kB chips)
3 A19 (512kB chips)
4 A15 (32kB chips)
This jumper selects the address at which the address logic switches between
the RAM chips. In effect, it defines the capacity of each RAM chip. The pin
assignment is as follows:
4
3 1 2
9.2 P2 — DMA Requests
Pin Assigment
1 Diskette controller request
2 DMA request 0 (to CPU)
3 Expansion socket request
4 DMA request 1 (to CPU)
5 SIO request
This header selects the sources for DMA requests. The Z180 core includes 2
DMA channels, which may be connected among 3 possible sources: diskette,
expansion socket, and serial IO channel. The standard boot code requires Pins
1 and 2 jumpered.
9.3 P3 — Flash Bootload Selector
Pin Assigment
1 RAM select from CPU
2 RAM socket 1 select
3 ROM socket select
4 ROM select from CPU
For normal use, jumper pins 1-2, 3-4. For ROM duplicating, jumper pins 1-3,
2-4. Pin 1 is at the bottom-right when holding the board with the battery to
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