GE GFK-0804B Memory Types and Addresses, Constants and Register Values in a Program, Memor y Map

1

Memory Types and Addresses

Memor y Map

Type Total

Non

Retentive

Retentive

Use for Timer

or Counter

Coil?

General

Purpose

Internal Coil?

Use as

General

Purpose

Register?

Use as

Indirect

Register

Reference?

I	256	1 ± 256		none	no	yes	no	no
O	256	1 ± 256		none	yes	yes	no	no
R	512	1 ± 384		385 ± 512*	no	yes	yes	yes
IR	256	1	± 256	no	notapplicable	notapplicable	yes	no
OR	256	1	± 256	no	notapplicable	notapplicable	yes	no
C	1017	1 ± 768		769 ± 1017	yes	yes	no	no

C

C

C

1

1

1

1018

1019

1021

0.1sec clock for use as input in application program (read only). Startup scan coil for use as input in application program. (read only)

Hold output coil for use in application program (read only).

Non-retentive and Retentive Registers

Data assigned to retentive memory is saved if power is removed from the Micro PLC.

Non-retentive registers are cleared to zero when power is removed, and when the

Micro PLC is switched from Stop mode to Run mode.

* Reserved Registers

Retentive Registers 501 through 512 should not be used in your application program; they are reserved.

Constants and Register Values in a Program

Many program functions for the Micro PLC use either constants, or variables in registers. Constant values are limited to 32757 maximum. Single-register variables are limited to 65535 maximum.

1-6 Micro PLC Programmer's Guide ± April 1994 GFK-0804B