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APPENDIX A: Jumper Descriptions and I/O addresses
Jumper Descriptions
JUMPER
DESCRIPTION
JP1
This allows the selection of one of the following baud rates: 300, 600, 1200,
4800, 9600 and 19,200.
OJ1
This is used to select the sources for the 8085's RST 5.5 and RST 6.5
interrupt
Display/Keypad controller interrupt request line when there is a connector
between pins 4 and 5, or, if a connector is between pins 3 and 4, it is
connected to the 8251 receiver ready line.
connected to the 8251 receiver ready line when there is a connector between
pins 2 and 3.
+5v.
This jumper can also be used to connect RST 5.5 and RST 6.5 to external
interrupt sources.
connected to RST 5.5.
0J2
This jumper is not implemented on the latest PCB revisions.
0J3
This selects one of the two memory maps which are as follows:
POSITION 'A' MEMORY MAP
SLOT 0
SLOT 1
8155 RAM
POSITION 'B' MEMORY MAP
SLOT 0
SLOT 1
8155 RAM
I/O Addresses
REFERENCE
8251 DATA REGISTER
8251 CONTROL REGISTER
8155 CONTROL REGISTER
PORT A
PORT B
PORT C
TIMER LOW
TIMER HIGH
EXPANSION I/O
inputs.
The
RST
Putting a connector between pins 1 and 2 connects RST 6.5 to
Pin 2 of the jumper is connected to RST 6.5 and pin 4 is
0000 TO 3FFF
4000 TO BFFF
C000 TO FFFF (only 256 bytes available)
0000 TO 7FFF
8000 TO FFFF
(not accessible)
I/O ADDRESS
DESCRIPTION
80 H
DATA INPUT/OUTPUT
81 H
CONFIGURATION
10 H
CONFIGURATION
11 H
OUTPUT PORT
12 H
INPUT PORT
13 H
ANALOG OUTPUT PORT
14 H
LOW ORDER TIMING BYTE
15 H
HIGH ORDER TIMING BYTE & CONTROL
C0 - FF H
EXPANSION CONNECTOR
5.5
interrupt
pin
The RST 6.5 interrupt pin is
82
is
connected
to
the
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