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Ladder Logic Elements and Instructions

870USE10110 July 2004 363

A Special STAT Instruction

Overview A special version of the STAT instruction has been developed to support Momentum

M1 CPUs. The STAT instruction accesses a specified number of words in a status

table in the CPU's system memory. Here vital diagnostic information regarding the

health of the CPU and the I/O bus I/O under its control is posted.

From the STAT instruction, you can copy some or all of the status words into a block

of registers or a block of contiguous discrete references.

This section describes the STAT instruction.

Avoid Discretes We recommend that you do not use discretes in the STAT destination node because

of the excessive number required to contain status information.

Specify Length The copy to the STAT block always begins with the first word in the table up to the

last word of interest to you. For example, if the status table is 20 words long and you

are interested only in the statistics provided in word 11, you need to copy only words

1...11 by specifying a length of 11 in the STAT instruction.

Diagram of STAT

Block

The STAT block includes a top node (for destination) and a bottom node (for length).

The STAT block is represented in the following illustration.

Top Node

Content

The reference number entered in the top node is the first position in the destination

block .....–i.e., the block where the current words of interest from the status table will

be copied. The reference may be:

The first 0x reference in a block of contiguous discrete outputs

The first 4x reference in a block of contiguous holding registers

Bottom Node

Content

The integer value entered in the bottom node specifies the number of registers or

16-bit words in the destination block where the current status information will be

written.

The length – i.e., number of words – in the status table will vary depending on

whether or not I/O bus I/O is being supported.

Without I/O bus, the STAT instruction is 12 words long.

With I/O bus, the instruction is 20 words long.

ON = operation successfulON copies specified number of

worlds from the status table

destination

STAT

length

1 2 ... 358 359 360 361 362 363 364 365 366 367 368 ... 375 376

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Momentum Modbus Plus 170 PNT Series Guia do Utilizador Página 363