1019
Serial Communications Instructions Section 3-24
Related Flags in the CPU Bus Unit Area
(n = CIO 1500 + 25
× unit number)
2201 hex Operation could not be performed during operation. (Operation dis-
abled because Unit is busy sending.)
2202 hex Operation could not be performed when stopped. (Operation dis-
abled because Unit is switching protocols.)
Word Bit Function
Port 1 Port 2
n+8 n+18 04 Overrun Error Flag
1: The reception buffer contained more than 259
bytes of data before RXDU(255) was executed.
Note: Once this error flag goes ON, it can be turned
OFF only by turning the power OFF and then ON
again or restarting the Board.
n+9 n+19 06 Reception Completed Flag
0: No data received or currently receiving data
1: Reception completed
0 → 1: The Board or Unit has received the specified
number of bytes.
1 → 0: RXD(235) or RXDU(255) was executed to write
the data from the buffer to a CPU Unit data area.
n+9 n+19 07 Reception Overflow Flag
0: The Board or Unit has not received more than
the specified number of bytes.
1: The Board or Unit has received more than the
specified number of bytes.
0 → 1: The Board or Unit received more data after data
reception was completed.
1 → 0: RXD(235) or RXDU(255) was executed to write
the data from the buffer to a CPU Unit data area.
n+10 n+20 05 Reception Counter
Indicates the number of bytes received in hexadecimal,
between 0000 and 0100 hex (0 to 256 decimal).
Code Meaning
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