Rockwell-automation 1747-DSN DISTRIBUTED I/O SCANNER Manual de usuario descargar pdf (Pagina 28)

Chapter 3

Configuration and Programming

3–10

The bits in the Communication Status Word(s) indicate whether or not the

scanner is communicating with each of the configured I/O blocks. Each bit

in the Communication Status Word(s) corresponds to an I/O block. If the

scanner is communicating with an I/O block, the corresponding bit in the

Communication Status Word is set to 1. The bits in the Communication

Status Word(s) can be used to:

• ensure that the I/O block(s) are communicating with the scanner before

any input data from the I/O block(s) is used by the SLC processor

program.

• have the SLC processor set an alarm or take appropriate action if

communication with an I/O block(s) is lost.

In addition to the Communication Status Bits for each individual I/O block,

the 30 I/O block Configuration has an Overall Communication Status Bit (bit

0 of word 0). This bit is set to 1 when all of the configured I/O blocks are

communicating with the scanner.

For example, if the scanner is configured for 4 I/O blocks, the Overall

Communication Status bit will be 1 when all four I/O blocks are

communicating. It will be set to 0 if any one of the I/O blocks is not

communicating. By monitoring this bit, the SLC processor can quickly

determine if communication with any configured I/O block has been lost.

The application example on page 3–11 illustrates a use of the

Communication Status Word.

The Control Word operates the same in both the 7 and 30 I/O block

Configurations. It is used to:

• configure the scanner for the exact number of I/O blocks that are on the

DIO Link (Number of I/O blocks, bits 0–4),

• start the scanner communicating with the I/O Blocks (Configuration Data

Valid Bit, bit 10)

• disable the I/O block outputs (Disable Output Bit, bit 9).

To start the scanner communicating with the I/O blocks when the SLC

processor enters run mode, the SLC processor program should:

• load the correct Number of I/O Blocks to bits 0 to 4

• set the Configuration Data Valid bit

Any further transitions of bits 0–4 (Number of I/O Blocks) while the SLC

processor is in run mode are ignored. Do not reset the Configuration Data

Valid bit to 0 during program execution. To change the number of I/O blocks

to which the scanner is communicating, the SLC processor must be taken out

of run mode.

Use of the Communication

Status Words

Use of the Control Word

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 39 40

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