Omron SYSMAC CJ - REFERENCE MANUAL 01-2008 Reference Manual page 1057

Serial Communications Instructions
Note
1018
RXDU(255) can not be executed while the Reception Completed Flag (bit 6
of n+9 or n+19, where n = CIO 1500 + 25
Reception Completed Flag as a normally open condition of RXDU(255).
An error will occur and the Error Flag will turn ON in the following cases.
• The Communications Port Enabled Flag for the specified logical port is
OFF when RXDU(255) is executed.
• The value of C is not within range.
• The value for N is not between 0000 and 0100 hex.
1. Reception Completed Flags (n = CIO 1500 + 25
Port 1: Bit 6 of n+9
Port 2: Bit 6 of n+19
2. Reception Counters (n = CIO 1500 + 25
Port 1: n+10
Port 2: n+20
3. Reception Overflow Flags (n = CIO 1500 + 25
Port 1: Bit 7 of n+9
Port 2: Bit 7 of n+19
4. Overrun Error Flags (n = CIO 1500 + 25
Port 1: Bit 4 of n+8
Port 2: Bit 4 of n+18
5. Transmission Error Flags (n = CIO 1500 + 25
Port 1: Bit 15 of n+8
Port 2: Bit 15 of n+18
6. Further data cannot be received until the received data is read from the
buffer with RXDU(255). When the Reception Completed Flag goes ON,
read that data promptly with RXDU(255) before more data is input to the
port.
7. When RXDU(255) is used to read data that was received at one of the Se-
rial Communications Unit's ports, the port's reception buffer is cleared after
RXDU(255) is executed. Consequently, RXDU(255) can not be executed
repeatedly to read a block of data in parts.
Section 3-24
CPU Unit
RXDU
RXDU
unit number) is ON. Program the
unit number)
unit number)
unit number)
unit number)
unit number)