Remote Technologies RPC-320 - Manual (Page 23)

DIGITAL AND OPTO PORTS SECTION 6
Page 6-1 RPC -320
Figure 6-1 Digital I/O
INTRODUCTION
Digital I/ O lines ar e used to inter face with op to-module
racks, switches, low current LED's, and other TTL
d e vi ce s. T h e RP C - 32 0 ha s 3 4 o f t he se li ne s. 8 T T L I/ O
lines go to a terminal strip. Additionally, there is one
high curr ent output and a n opto-isolated inp ut. R efer 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 con nector, J3, is inte nded to inter face to opto
racks or other TT L devices. 8 of these lines are high
curr ent outputs, capable of sink ing 75 to 200 m a. O pto
m o d ul e s o n an o pt o r a c k s e ns e pr e se n ce o f A C o r D C
v o lt a ge s or s w it c h t he m .
L8 at P2 is a "zero" ohm FE T switch. It is intended for
switching L ED b ack lighting on a n LC D display. This
line may also be used to switch high current, high
voltage power . It can sw itch up to 2 amps.
ISOA/B is used as an isolated input as well as an
interr upt.
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 softwar e comm ands support the digital I/O ports.
ON L INE br anches to a subroutine w hen a line changes.
ON C OUN T counts the number of high to low
transitions at a digital line. Maxim um coun ting rate is
about 95 Hz. T hese 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 CONF IG
LINE comm and. See Appendix A for information.
WARNING:
When using CON FIG 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 C ONF IG
L I N E 0 i s e x ec u te d . R ef e r t o C O N F I G L IN E
command in Appendix A for more inform ation.
Digital Por t J3
This port is used to interface opto modules (using the
MP S series racks), drive small r elays, solenoids,
m o to r s, o r la m ps , a nd p ro v id e ge n er a l p u rp o se T T L I/ O
to other logic devices or mechanical switches. The
LIN E com mand is use d to access an d control this p ort.
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 progr amm ed as one gr oup of 8 inputs
or outputs or as two groups of four lines (upper and
lower C). T he four lines in upper and lower C can each
be prog ram med as a ll inputs or outp uts. R efer to T able
6-1 to determine the opto channel or J3 pin number for a
port. U se CON FIG LIN E 100 (Appendix A) to
configure por ts 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 dr ive opto
modules. P ort 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