GE PACSystems RX7i Reference Manual page 236

Return Data Format for the Read String Function
The return data consists of the number of characters actually read, the number of characters still
available in the input buffer after the read is complete (if any), and the actual input characters:
Address Number of characters actually read
Address + 1 Number of characters still available in the input buffer, if any
Address + 2 first two characters (first character is in the low byte)
Address + 3 third and fourth characters (third character is in the low byte)
Address + n subsequent characters
Operating Notes for Read String
If the input data memory type parameter is specified to be a word memory type, and if an odd number
of bytes is actually received, then the high byte of the last word to be written with the received data is
left unchanged.
As data is received from the serial port it is placed in the internal input buffer. If the buffer becomes full,
then any additional data received from the serial port is discarded and the Overflow Error bit in the Port
Status word (See Read Port Status Function) is set.
GFK-2222AD
Chapter 6. Serial I/O, SNP & RTU Protocols
April 2018 225