GE GFK-1541B manual Bits Bit words AI1 257 16641 AQ1 16897 29185 61825

Appendix

E

Translating PLC CPU Reference Addresses to Modbus Register Addresses for the IC693CMM321

The Modbus/TCP protocol defines operations on a set of reference tables (Register, Input Register, Input Discrete, and Coil); these Modbus tables differ from the PLC reference tables within the PLC CPU (%I, %AI, %Q, %AQ, %M, and %R). To implement the Modbus/TCP protocol, the IC693CMM321 maps each of the Modbus tables into one or more PLC CPU tables (see Table below). The IC693CMM321 makes no distinction between the Register and Input Register tables.

IC693CMM321	Modbus Register	Modbus Input	Modbus Input	Modbus Coil
Internal Tables	Table	Register Table	Discrete Table	Table
	(4xxxxx)	(3xxxxx)	(1xxxx)	(0xxxx)
%I1 – 4096	1 – 256	1 – 256	1 – 4096	---
(bits)	(16-bit words)	(16-bit words)	(bits)
%AI1 – 16384	257 – 16640	257 – 16640	---	---
(16-bit words)	(16-bit words)	(16-bit words)
%Q1 – 4096	16641 – 16896	16641 – 16896	---	1 – 4096
(bits)	(16-bit words)	(16-bit words)		(bits)
%AQ1 – 12288	16897 – 29184	16897 – 29184	---	---
(16-bit words)	(16-bit words)	(16-bit words)
%R1 – 32640	29185 – 61824	29185 – 61824	---	---
(16-bit words)	(16-bit words)	(16-bit words)
%M1 – 4096	61825 – 62080	61825 – 62080	---	---
(bits)	(16-bit words)	(16-bit words)
Mapping Code	65535	65535	---	---
(16-bit word)	(16-bit word)	(16-bit word)

Table E-1 - Modbus Register / IC693CMM321 Reference Table Translation

Note: The Mapping Code is a read-only address. A client may read this address to determine the mapping in use without knowing what type of device this is. The IC693CMM321 will return a 1 when this register is read, indicating that the above mapping in is use.

GFK-1541B E-1