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DIGITAL LINES CHAPTER 6

Page 14 RPC-150

Figure 6-1 Digital I/O

INTRODUCTION

Digital I/O lines ar e used to inter face with opto-module

racks, switches, low current LED's, and other TTL

devices. The RP C-150 h as 47 of these line s available

through J2 and J3. Seven of these lines are high current

outputs, capable of sinking 75 to 200 ma. Eight lines on

J2 are shared by the keypad connector, J5. When the

keypad is used, 8 of the 47 lines are not available.

Eight, 16, or 24 position opto racks are connected to J2

or J3. These opto racks 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 current is 3 amperes.

WARNING:

Apply power to the RPC -150 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-150 first, contact

technical support for suggestions appropriate to your

application.

DIGITAL I/O PORT

Digital I/O lines on the RPC-150 are supplied by an

82C55 chip. The chip' s lines go to connectors J2 and

J3.

The lines on J2 and J3 are divided into 3 eight bit

groups. Ports 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). The four lines in upper and lower C can

each be pr ogram med as a ll inputs or outputs. P ort B, bit

7 on J2 must be used as an output.

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 LINE, OPTO,

INP, and OUT statements. LINE r eads or writes to a

port based on the connector pin number. OPTO 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 address for J2 is 512 and J3 is 0 when using

CONFIG PIO , INP, and OUT statements. CONFIG

PIO statement is used to configure the 8255 lines. Upon

reset, lines are configured for inputs. Use CONFIG PIO

to configure lines for outputs and inputs.

J2 and J3 are accessed using LIN E or O PTO statements

according to the table below.

Connector LINE # OPTO rack

No terminal position

J3 1 - 25 0 - 23

J2 101 - 124 100 - 122

J2 port B is connected to a high current sink through

U13. See "High current output" later in this chapter.

Line 107 is not available.

J2 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 and J3 are pulled 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 J2 can be used as high current driver s.

These outputs will switch loads to ground. Outputs are

controlled by Port B on the 82C55. Its address is 513.

Port B bits 0-6 are used to control the high current por t.

Logic outputs from this port are inverted. That is, when

a 1 is written to the high cur rent por t, the output is

switched on and goes low.

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 25 26

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