Remote-processing RPC-52 Manuel d'utilisateur télécharger pdf (Page 20)

DIGITAL AND OPTO PORTS CHAPTER 6

Page 18

Figure 6-2 Inductive load protection

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

outputs sink 15 m a at 1.0V. This will dr ive opto

modules. Port B is connected to a high current sink

through U 20. See "H igh curr ent output" later in this

chapter.

Digital I/O lines at J4 are pulled up to + 5 volts or

ground through a 10K resistor pack using jumper W9.

Jumper W9 for pull up or down configuration is as

follows:

W9[1-2] Pull up

W9[2-3] Pull down

Setting W9 for pull up makes interfacing to switches and

"open collector" TTL devices easy . See "Inter facing to

Switches and other devices" below.

Digital I/O commands

The CONFIG LINE statement is used to configure the

82C55 ports. This statement stores input and output

parameters in serial EEPROM for recall at power up or

reset. CON FIG LINE should not be executed very often

as the serial EEP ROM has a limited number of write

cycles (100,000). F actory default is: P ort A - Inputs,

Port B - Outputs, Port C - Inputs.

LINE function and statement is used with opto m odules.

It accesses a module according to the position number

printed on the board. L ines are number ed from 100 to

123. The opto m odule num ber used in this comm and is

computed by adding 100 to the board position number.

The LIN E B function and statement is used to access

digital I/O lines 8 bits at a time. T he address for port A

is 0, B is 1, and C is 2. The bank number is 3.

LINE # function and statement accesses lines according

to the pin number at J4. Lines are num bered from 101

to 125. The line number used in this command is

computed by adding 100 to the connector pin number.

Line 102 is not allowed as it is the + 5V supply. See

table 6-1 to cor respond a pin number to a por t and opto

rack position.

LINE, LINE B and LIN E # re turn the ' true' logic level.

A ' 1' indicates + 5 volts or high and a '0' is low or

ground. LINE B and LINE # output true logic levels.

LINE, however, outputs inverted logic. In order to turn

on an opto module, a line must go low. However,

turning on a module using LINE, you must specify a

'1'.

High current output

Eight lines at J4 can be used as high current driver s.

These outputs will switch loads to ground. Outputs are

controlled by Port B on the 82C55.

Logic outputs are inverted. That is, when a 1 is written

to the high current port, the output is switched on and

goes low.

The output driver chip, U 20, can be replaced with a DIP

shunt jumper so it is like the other lines at J4.

NOTE: Outputs at the high current lines are not

compatible with TTL logic levels and should not

be used to drive other logic devices.

Each of the high current outputs can sink 500 ma at 50V.

However, package dissipation will be exceeded if all

outputs are used at the maximum rating. The following

conservative guidelines assume the number of outputs

are on simultaneously:

# of outputs Maximum current

on per output

1 500 ma

2 400 ma

3 275 ma

4 200 ma

5 160 ma

6 135 ma

7 120 ma

8 100 ma

The ther mal time constant of the package is very short,

so the number of outputs that are on at any one time

should include those that overlap even for a few

milliseconds.

Incandescent lamps have a "cold" current of 11 times its

operating current. Lamps requiring more than 50 ma

should not be used.

Protection diodes m ust be used with inductive loads.

Refer to figure 6-2

Do not parallel outputs for higher drive. This results in

damage since outputs do not share current equally.

The outputs at U20 are pulled either up or down through

10K resistors, according to the status of jumper block

W9.

Interfacing digital I/O to an opto-module rack

I/O lines can be interfaced to an MPS-8, 16, or 24

position opto module rac k. L ines not going to an opto

module connect to a screw terminal on the MPS-XX

series boards. This feature allows you to connect

switches or other TTL type devices to the digital I/O

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Remote-processing RPC-52 Manuel d'utilisateur Page 20

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