Vi-2-13. Ppi - Canon A-200 series Service Manual

VI-2-13. PPI
The A-200 employs the 8255 as the PPI. This LSI is used in MODEO. In this mode, the port A,
port B, upper 4 bits of port C and lower 4 bits of port C can be assigned as either of input ports
or output ports independently.
In the A-200, the port A and upper and lower bits of the port C are used as inputs, and the port
B as outputs.
Table 6-8 shows the port assignments.
1/0
Address
Terminal
60 PAO
PA1
PA2
PA3
PA4
PA5
PA6
PA7
61 PBO
PB1
PB2
PB3
PB4
PB5
PB6
PB7
62 PCO
PC1
PC2
PC3
PC4
PC5
PC6
PC7
1/0
PB7=L
I Key Data (LSB)
I
Key Data (LSB)
I Key Data (LSB)
I
Key Data (LSB)
I
Key Data (LSB)
I Key Data (LSB)
I Key Data (LSB)
I Key Data (LSB)
0
PIT G2 terminal
0
Speaker data
0
Not used
0
Not used
Description
PB7=H
IPL 5-1/4" disk drive*
8087 installed
System Memory Size
System Memory Size
Display Type
Display Type
Number of disk drive
Number of disk drive**
0
System Memory Parity Enable
0
Optional Memory Parity Enable
0
Soft Reset for Keyboard Unit
0
Enable K/B data or DIP Switch Status
I Optional RAM Size
I Optional RAM Size
I Optional RAM Size
I
Optional RAM Size
I Not used
I PIT OUT 2 terminal
I Optional Memory Parity Check
I System Memory Parity Check
* Pull up to Vee ** Pull down to ground
Table 6-8
73