MBM_FC03_HoldingRegRdFP() - Modbus-M

This function is called from YOUR application code to read 32-bit floating-point registers from a Modbus slave.

Prototype

CPU_INT16U  MBM_FC03_HoldingRegRdFP (MODBUS_CH  *pch, 
                                     CPU_INT08U  slave_node,
                                     CPU_INT16U  start_addr,
                                     CPU_FP32   *p_reg_tbl,
                                     CPU_INT16U  nbr_regs);

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 read the registers from. This can be a number between 1 and 255 but needs to match the number assigned to the slave node.

start_addr

specifies the start address of the floating-point holding registers. This can be from MODBUS_CFG_FP_START_IX to 65535 (of the slave) and assumes that you enabled floating-point support by setting MODBUS_CFG_FP_EN to DEF_ENABLED in mb_cfg.h in the slave.

p_reg_tbl

is a pointer to an array of 32-bit IEEE-754 format floating-point values that will receive the value of all the registers you are reading. The size of the array needs to be at least nbr_regs.

nbr_regs

specifies the number of registers you want to read from the slave.

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.

Notes / Warnings

The floating-point format corresponds to the Daniels Flow control extensions. Specifically, a register is assumed to be 32 bits and uses the IEEE-754 format.

Floating-support must have been enabled in the slave you are communicating with and, the start address of the floating-point registers (MODBUS_CFG_FP_START_IX) corresponds to that of the slave.

Called By

Your Modbus master application.