Octagon PC-500, User Manual

Page: 95 / 233

11-4
EZ I/O PC-500 user’s manual
Table 11-4 Reading the EZ I/O port
I/O range select A
(bit 5)
I/O range select B
(bit 4) EZ I/O
base address
0 1 130h
0 0 150h
1 1 330h*
1 0 350h
* = default
≡
Configuring and programming the EZ I/O ports
Located at J11 on the PC-500, the digital I/O connector is program-
mable by an Octagon EZ I/O digital chip. The EZ I/O chip has three
ports with eight parallel I/O lines (bits) per port. This port can use one
of four base I/O addresses. All lines can be individually programmed as
all inputs, all outputs, or individually as inputs or outputs. You can
alter which bits are inputs or outputs by writing a control command to
the control register of the EZ I/O port. When a line is configured as an
output, it can sink a maximum of 15 mA at 0.4V or can source 15 mA at
2.4V. On powerup and software or hardware reset, all digital I/O lines
at J11 reset as inputs.
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 "2" 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.