Chapter 6. Serial I/O, SNP & RTU Protocols
224
PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual
GFK-2222AD
6.2.15
Read String Function (4403)
This function causes characters to be read from the specified port until a specified terminating character
is received. The characters are read from the internal input buffer and placed in the specified input data
area.
The function returns both the number of characters retrieved and the number of unprocessed characters
still in the input buffer. If zero characters of input are requested, only the number of unprocessed
characters in the input buffer is returned.
If the terminating character is not in the input buffer, the status of the operation is not complete until
either the terminating character has been received or the time-out interval expires. In either of those
conditions, the port status indicates the reason for completion of the read operation.
If the time-out interval is set to zero, the COMMREQ remains pending until it has received the requested
string, terminated by the specified end character.
If this COMMREQ fails for any reason, no data is returned to the input data area. Any data that has not
been read from the internal input buffer remains, and it can be retrieved with a subsequent read request.
Example Command Block for the Read String Function
Value
(decimal)
Value
(hexadecimal)
Meaning
Address
0005
0005
Data block length
A1
0000
0000
NOWAIT mode
A2
0008
0008
Status word memory type (%R)
A3
0000
0000
Status word address minus 1 (%R0001)
A4
0000
0000
Not used
A5
0000
0000
Not used
A6
4403
1133
Read string command
A7
0030
001E
Read time-out (30 seconds)
A8
0013
000D
Terminating character (carriage return): must be
between 0 and 255 (0xFF), inclusive
A9
0008
0008
Input data memory type (%R)
A10
0100
0064
Input data memory address (%R0100)
