Chapter 6. Serial I/O, SNP & RTU Protocols218 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222AD6.2.11 Cancel COMMREQ Function (4399)This function cancels the current operations in progress. It can be used to cancel both read operationsand write operations.If a read operation is in progress and there are unprocessed characters in the input buffer, thosecharacters are left in the input buffer and available for future reads. The serial port is not reset.Example Command Block for the Cancel Operation FunctionValue(decimal)Value(hexadecimal)MeaningAddress 0002 0002 Data block length (2)Address +1 0000 0000 NOWAIT modeAddress +2 0008 0008 Status word memory type (%R)Address +3 0000 0000 Status word address minus 1 (%R0001)Address +4 0000 0000 Not usedAddress +5 0000 0000 Not usedAddress +6 4399 112F Cancel operation commandAddress +7 0001 0001 Transaction type to cancel1 - All operations2 - Read operations3 - Write operationsOperating NotesRemote COMMREQs that are cancelled due to this command executing will return a COMMREQ statusword indicating request cancellation (minor code 12H).CautionIf this COMMREQ is sent in either Cancel All or Cancel Writemode when a Write Bytes (4401) COMMREQ is transmitting astring from a serial port, transmission is halted. The positionwithin the string where the transmission is halted isindeterminate. In addition, the final character received by thedevice to which the CPU is sending is also indeterminate.
