Octagon PC-510, User Manual

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11-5
PC-510 user’s manual EZ I/O
Programming the EZ I/O
Follow these steps to program the EZ I/O chip:
1. Configure the EZ I/O port bit directions, either as inputs or outputs.
2. Write to port A, B, or C with the desired level or read the bit level from
the desired port.
Configuring the EZ I/O
Follow these steps to configure the EZ I/O chip
1. Write a "3" to the control register (base a 3). This places the I/O
chip in “direction” mode:
(default base address = 330h)
OUT 333h, 2 (control register, direction mode)
2. Set the direction of each bit. A "0" written to the corresponding line
indicates an input and a "1" bit indicates an output. Each bit corre-
sponds to the equivalent I/O line.
Table 11-6 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 re 3). This places the I/O
chip back into “operation” mode:
OUT 333h, 3 (control register)