DIGITAL AND OPTO PORTS SECTION 6
Page 6-1 RPC-320
Figure 6-1 Digital I/O
INTRODUCTION
Digital I/O lines are used to inter face with opto-module
racks, switches, low current LED's, and other TTL
devices. The RPC-320 has 34 of these lines. 8 TTL I/O
lines go to a terminal strip. Additionally, there is one
high curr ent output and an opto-isolated input. Refer to
the figure below for the location of these lines.
Eight lines at P6 are intended for general purpose TTL
I/O such as switches, level sensors or to drive other
devices.
A 24 line connector, J3, is intended to interface to opto
racks or other TTL devices. 8 of these lines are high
current outputs, capable of sinking 75 to 200 ma. O pto
modules on an opto rack sense presence of AC or DC
voltages or switch them.
L8 at P2 is a "zero" ohm FET switch. It is intended for
switching LED back lighting on an LCD display. This
line may also be used to switch high current, high
voltage power. It can switch up to 2 amps.
ISOA/B is used as an isolated input as well as an
interrupt.
In addition to the 24 I/O lines from J3, the display port
can be used as digital I/O. Refer to Chapter 8 for more
information.
WARNING:
Apply power to the RPC-320 before applying a
voltage to the digital I/O lines to prevent current
from flowing in and damaging devices. If you
cannot apply power to the RPC-320 first, contact
technical support for suggestions appropriate to your
application. Power may be applied to ISOA/B at
any time.
Several software comm ands support the digital I/O ports.
ON LINE br anches to a subroutine when a line changes.
ON COUNT counts the number of high to low
transitions at a digital line. Maxim um counting rate is
about 95 Hz. These commands simplify design and
greatly speed up execution. See Appendix A for more
information.
DIGITAL I/O PORTS
All ports use an 82C55 for I/O. Lines are accessed
using LINE or LINEB commands. Lines at J3 and P6
are configured for inputs or outputs using the CONFIG
LINE command. See Appendix A for information.
WARNING:
When using CONFIG LIN E, output lines go low
momentarily (less than 10 micro-seconds) until they
are set high again as per the data in the command
line. Some other lines are affected when CONFIG
LINE 0 is executed. Refer to CONFIG LINE
command in Appendix A for more information.
Digital Port J3
This port is used to interface opto modules (using the
MPS series racks), drive small relays, solenoids,
motors, or lamps, and provide general purpose TTL I/O
to other logic devices or mechanical switches. The
LINE command is used to access and control this port.
The lines on J3 are divided into 3 eight bit groups from
an 82C55. Ports A and B are configured as all inputs or
outputs. Port C is programmed as one gr oup of 8 inputs
or outputs or as two groups of four lines (upper and
lower C). The four lines in upper and lower C can each
be programmed as all inputs or outputs. Refer to Table
6-1 to determine the opto channel or J3 pin number for a
port. Use CONFIG LIN E 100 (Appendix A) to
configure ports A, B, and C for inputs or outputs.
When a line is configured as an output, it can sink a
maximum of 2. 5 ma at 0.4V and can source over 2.5
ma. Outputs sink 15 ma at 1. 0V. This will drive opto
modules. Port B is connected to a high current sink
through U12. See "High current output" later.
Digital I/O lines at J3 m ay be pulled up to + 5 volts or to
