SYNOPSIS
*int modbus_reply_exception(modbus_t *ctx, const uint8_t *req, unsigned int exception_code);
DESCRIPTION
The modbus_reply_exception() function shall send an exception response based on the exception_code in argument.
The libmodbus provides the following exception codes:
- • MODBUS_EXCEPTION_ILLEGAL_FUNCTION (1)
- • MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS (2)
- • MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE (3)
- • MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE (4)
- • MODBUS_EXCEPTION_ACKNOWLEDGE (5)
- • MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY (6)
- • MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE (7)
- • MODBUS_EXCEPTION_MEMORY_PARITY (8)
- • MODBUS_EXCEPTION_NOT_DEFINED (9)
- • MODBUS_EXCEPTION_GATEWAY_PATH (10)
- • MODBUS_EXCEPTION_GATEWAY_TARGET (11)
The initial request req is required to build a valid response.
RETURN VALUE
The modbus_reply_exception() function shall return the length of the response sent if successful. Otherwise it shall return -1 and set errno.
ERRORS
EINVAL
- The exception code is invalid
AUTHORS
The libmodbus documentation was written by Stéphane Raimbault <m[blue][email protected]m[][1]>
NOTES
- 1.
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