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Modbus Commands

2-33

SIMATIC TI505/TI500 MODNIM User Manual

Code

15 allows the host computer to write multiple coils. When this

command is given, successive coils are changed by an associated bit pattern

to the indicated state, where each bit indicates: 1 = ON

0 = OFF

Addressing is sequential up to the maximum memory size for a particular

secondary

. The maximum number of coils that can be addressed with one

command is 800. If more are given, the whole command will be rejected with

an Exception code 03.

The broadcast address (00) can be used to change the same coils in all

networked programmable controllers.

[This command is equivalent to TIW

Y Primitive 30 using data types 04, 07

(Y unpacked, packed) or data types 05, 08 (C unpacked, packed), depending

on the position of configuration Switch 10.]

Because

of differences in memory mapping between Modbus PLCs

and SIMA

TIC TI PLCs, you should be quite certain of the effects of

the broadcast command before issuing it.

Example:

Request: 07 0F 0012 000C 02 DC08 XXXX

Checksum (XXXX)

Coil status (DC08)

Number of bytes (02)

Number of coils (000C)

Start coil address (0012)

Function code 15 (0F hex)

Slave address (07)

Figure 2-27 Write

Multiple Coils Example — Request

Code 15 — W

rite

Multiple Coils

WARNING

1 2 ... 59 60 61 62 63 64 65 66 67 68 69 ... 90 91

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Siemens SIMATIC TI505 Bedienungsanleitung Seite 64