Rockwell-automation 1771-IFE , D17716.5.90 USER MNL. ANALOG INPUT Modu Manual de usuario descargar pdf (Pagina 26)

Module Programming

Chapter 3

3-2

The PLC-2 program example regulates when each block transfer will be

initiated to eliminate problems caused by limited regulation of

bidirectional block transfers. Both storage bits are needed, as shown in the

example, to accomplish this task in all PLC-2 systems, local or remote,

with long or short program scans. Therefore, the program as shown is the

minimum required. Note that PLC-2 processors that do not have the block

transfer instruction must use the GET-GET block transfer format which is

outlined in Appendix E.

Figure 3.1

PLC2

Family Sample Program Structure

Block Transfer Read

[1] You can replace the pushbutton with a timer done" bit to initiate the block transfer

ENABLE

DONE

Pushbutton [1]

Bit A

Done Bit Pushbutton [1]

Block Transfer Write

Done Bit

Storage

Block Transfer Write

Bit A

Done Bit

Storage

Bit B

Done Bit

Power-up

Block Transfer Read

Bit B

Bit

Power-up

Bit

Storage

BTR Done

ENABLE

DONE

Storage

Bit A

Bit

Bit B

Power-up

Bit

Storage

ENABLE

DONE

Storage

Bit B

Bit A

write on a timed basis. You can also use any storage bit in memory.

BLOCK XFER READ

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

XXX

RGS

YYYY - XXX

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

XXX

YYYY - XXXX

FILE R:

RATE PER SCAN

XXX - XXX

XXX

BLOCK XFER WRITE

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

XXX

RGS

XXXX - XXXX

Storage

10954I

Rung 1

Block transfer read buffer: the

filetofile move instruction holds the

block transfer read (BTR) data (file A)

until the processor checks the data

integrity. If the data was successfully

transferred, the processor energizes

the BTR done bit, initiating a data

transfer to the buffer (file R) for use in

the program.

If the data is corrupted during the BTR

operation, the BTR done bit is not

energized and data is not transferred to

the buffer file. In this case, the data in

the BTR file will be overwritten by data

from the next BTR.

Rungs 2 and 3

These rungs provide for a userinitiated

block transfer write (BTW) after the

module is initialized at powerup.

Pressing the pushbutton locks out BTR

operation and initiates a BTW that

reconfigures the module. Block transfer

writes will continue for as long as the

pushbutton remains closed.

Rungs 4 and 5

These rungs provide a readwriteread"

sequence to the module at powerup.

They also make sure that only one

block transfer (read or write) is enabled

during a particular program scan.

Rungs 6 and 7

These rungs are the conditioning block

transfer rungs. Include all the input

conditioning shown in the example

program.

BTR

BTW

PLC2 Programming

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