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This function is called from YOUR application code to write to a single coil on a Modbus slave.

Prototype

CPU_INT16U  MBM_FC05_CoilWr (MODBUS_CH  *pch, 
                             CPU_INT08U  slave_node,
                             CPU_INT16U  slave_addr,
                             CPU_BOOLEAN coil_val);

Arguments

pch

is a pointer to the channel (returned by MB_CfgCh()). This pointer specifies onto which channel the Modbus master will be communicating on. Of course, ‘pch’ must have been configured as a Master when you configured the channel.

slave_node

specifies the slave ‘node address’ that you desire to change the coil value. This can be a number between 1 and 255 but needs to match the number assigned to the slave node.

slave_addr

specifies the address of the coil that you want to change. This can be from 0 to 65535.

coil_val

is the desired value of the coil and can be either: MODBUS_COIL_OFF or MODBUS_COIL_ON.

Returned Value

MODBUS_ERR_NONE

if the call was successful.

MODBUS_ERR_RX

if a response was not received from the slave within the timeout specified for this channel (see MB_CfgCh()).

MODBUS_ERR_SLAVE_ADDR

If the transmitted slave address doesn't correspond to the received slave address

MODBUS_ERR_FC

If the transmitted function code doesn't correspond to the received function code

MODBUS_ERR_BYTE_COUNT

If the expected number of bytes to receive doesn't correspond to the number of bytes received.

MODBUS_ERR_COIL_ADDR

If you specified an invalid coil address.

Notes / Warnings

None

Called By

Your Modbus master application.