Octagon PC-500, User Manual

Page: 96 / 233

11-5
PC-500 user’s manual EZ I/O
Table 11-5 EZ I/O port byte
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
EZ I/O port
I/O line
x 7
x 6
x 5
x 4
x 3
x 2
x 1
x 0
For example, writing 00011100 to port C (base a 2) will config-
ure port C I/O lines 0, 1, 5, 6, and 7 to be inputs and lines 2, 3, and 4 to
be outputs:
OUT 332h, 1Ch (00011100 binary = 1C hexadecimal)
3. Write a "3" to the control register (base r3). This places the I/O
chip back into “operation” mode:
OUT 333h, 3 (control register)
Writing and reading from EZ I/O
Writing to or reading from the desired EZ I/O port is accomplished with
single program statements:
1. To write a bit pattern to the desired EZ I/O port:
OUT 332h, FFh
All bits of port C go high; all input bits are unaffected.
2. To read a bit pattern from the desired EZ I/O port:
PORTC = INP(332h)
The byte read from port C is assigned to variable port C.
EZ I/O output program examples
To configure ports A, B, and C as all outputs, issue the commands:
OUT 333h, 2 ‘Direction’ Mode
OUT 330h, FFh ‘PortA’
OUT 331h, FFh ‘PortB’
OUT 332h, FFh ‘PortC’
OUT 333h, 3 ‘Operation’ Mode