Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Bedienungsanleitung PDF herunterladen (Seite 218)

13–3PLC Addressing

Publication

17706.5.16 - October 1996

PLC2 Physical Addressing

PLC-2 processors use physical addresses that are directly related to

the logical addresses. To convert a logical address to its

corresponding physical address:

1. Move bit 7 of the logical address to bit position 1.

2. Shift bits 1 through 6 to the left one position.

The following figure illustrates the conversion process for logical

word address 121. Remember that the logical PLC-2 address is a

byte address, so the physical address is also a byte address.

Converting a PLC2 Logical Address to a Physical Address

00 00000 010 110 0 0 0

Bit (octal)

High byte Low byte

17 16 1115 14 13 12 10 7 6 154 3 2 0

00 00000 001 100 0 1 0

Shift bit values 1 through 6

to the left one position.

PLC2 word address = 121 octal

logical byte address = 242 octal

physical byte address = 0046 hex

To send a physical read or physical write to a PLC-2 node, put the

PLC-2 physical address in the ADDR field of the command.

Be sure to encode the low byte of the physical address as the first

byte in the ADDR field.

1774PLC Physical Addressing

The 1774-PLC controllers use physical addresses that are exactly the

same values as the corresponding logical addresses. Remember that

the logical address is a byte address, so the physical address is also a

byte address. For example, the logical byte address of the 17th word

in PLC memory is 32 decimal, and the physical address is 32

decimal.

To send a physical read or write command to a 1774-PLC node,

put the 1774-PLC physical address in the ADDR field of the

command message packet. Be sure to encode the low byte of the

physical address as the first byte in the ADDR field.

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Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Bedienungsanleitung Seite 218