Chapter 6. Serial I/O, SNP & RTU ProtocolsGFK-2222AD April 2018 2056.1.6 Example COMMREQ Command Blocks for Serial Port Setup functionThe following COMMREQ command blocks provide examples for configuring the various protocols. Allvalues are in decimal unless followed by an H indicating hexadecimal.Note that an example is not provided for Message Mode, but it can be setup with a command blocksimilar to the one for Serial I/O, with a value of 7 for the protocol selector.Example COMMREQ Command Block for Configuring SNP ProtocolValues MeaningAddress 16 Data Block LengthAddress + 1 0 = No Wait (WAIT mode not supported) WAIT/NOWAIT FlagAddress + 2 0008 = %R, register memory Status Word Pointer MemoryTypeAddress + 3 Zero-based number that gives the address of the COMMREQstatus word (for example, a value of 99 gives an address of100 for the status word)Status Word Pointer OffsetAddress + 4 not used Idle Timeout ValueAddress + 5 not used Maximum Communication TimeAddress + 6 FFF0H Command Word (serial portsetup)Address + 7 1 = SNP ProtocolAddress + 8 0 = Slave Port ModeAddress + 9 See COMMREQ Command Block Parameter Values. Data RateAddress + 10 0 = None, 1 = Odd, 2 = Even ParityAddress + 11 not used (SNP always chooses NONE by default) Flow ControlAddress + 12 0 = None, 1 = 10ms, 2 = 100ms, 3 = 500ms Turnaround DelayAddress + 13 0 = Long, 1 = Medium, 2 = Short, 3 = None TimeoutAddress + 14 not used (SNP always chooses 8 bits by default) Bits Per CharacterAddress + 15 0 = 1 Stop Bit, 1 = 2 Stop bits Stop BitsAddress + 16 not used InterfaceAddress + 17 not used (SNP always chooses 4-wire mode by default) Duplex ModeAddress + 18 user-provided 82 Device identifier bytes 1 and 2Address + 19 user-provided 82 Device identifier bytes 3 and 4Address + 20 user-provided 82 Device identifier bytes 5 and 6Address + 21 user-provided 82 Device identifier bytes 7 and 882 The device identifier for SNP Slave ports is packed into words with the least significant character in the least significant byteof the word. For example, if the first two characters are “A” and “B,” the Address + 18 will contain the hex value 4241.
