Remote Processing RPC-2300 - Manual (Page 18)

DIGITAL LINES CHAPTER 6
Page 16 RPC-2300
F i gu r e 6 -1 D ig it al 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
devices. The SBS-23 00 has 48 of the se lines available
through J2 and J3. Eight of these lines are high current
outputs, capable of sinking 75 to 200 ma. Eight lines on
J3 are shared by the keypad connector, J5. When the
keypad is used, 8 of the 48 lines are not available.
Eight, 16, or 24 position opto racks are connected to J2
or J3. These opto rac ks accept G4 ser ies opto modules.
G4 series opto modules are used to sense the presence of
AC or D C voltages or switch them. Maximum
switching curr ent is 3 ampere s.
WARNING:
Apply power to the SBS-2300 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 SBS-2300 first, contact
technical support for suggestions appropriate to your
application.
DIGITAL I/O PORT
Digital I/O lines on the SBS-2300 are supplied by an
82C55 chip. T he chip' s lines go to connectors J2 and
J3.
The lines on J2 and J3 ar e divided into 3 eig ht bit
groups. P orts A and B can be configured as all inputs or
outputs. Port C can be programm ed as one group 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 progr amme d as all 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 at 2.4V. Outputs sink 15 mA at 1.0V.
J2 and J3 are accessed using CAMBASIC II LINE,
OPTO , IN P, and OUT statements. LINE r eads or
writes to a port base d on the conne ctor num ber. LINE is
generally used with the STB-26 board. OP TO reads or
writes to an opto module based on its position in an MPS
opto rack . IN P and O UT a ccess a byte o f data at a por t.
The base I/O addr ess for J2 is 0 and J3 is 64 when using
INP, OUT, and CON FIG PIO statements. CO NFIG
PIO statement is used to configure the 8255 lines for
inputs and outputs. Upon reset, lines are configured for
inputs.
J2 and J3 ar e accessed using LIN E or O PTO statements
according to the table below.
Connector LINE # OPTO r ack
N o terminal position
J2 1-25 0-23
J3 101 - 125 100 - 123
LINE #' s access that pin number on J2 or J3. LIN E # 2
or 102 are not valid. L ine 2 is + 5 volt supply.
J3, port A is connected to a high current sink through
U20. See High current output later in this chapter.
J3 port C is shared with the keypad port J5. If you are
using a keypad through J5, these 8 lines are not
available.
Pull up resistors
Digital I/ O lines at J2 an d J3 are p ulled up to + 5 volts
through a 10K resistor pack.
These pull ups makes interfacing to switches and "open
collector" TTL devices easy . See "Inter facing to
Switches and other devices" below.
High current output
Eight lines at J3 can be used as high cur rent driver s.
These outputs switch loads to ground. Outputs are
controlled by Port A on the 82C55. Its address is 64.
Logic outputs from this port are inverted. That is, when