Omron CP - PROGRAMMING MANUAL 05-2007 Programming Manual page 872

Serial Communications Instructions
Example: Flag Operation
Serial
Communications
Unit
CPU Unit
Related Flags in the CPU Bus Unit Area
(n = CIO 1500 + 25
Word
Port 1 Port 2
n+8 n+18 04
n+9 n+19 06
n+9 n+19 07
n+10 n+20 05
The following diagram shows the operation of RXDU(255) and related flags.
Reception processing
ON
Reception Completed Flag
(Bit 6 of n+9 or n+19,
n = CIO 1500 + 25 x unit number)
OFF
RXDU(255)
Communications Port
ON
Enabled Flag
(A20200 to A20207 correspond to
communications ports 0 to 7.)
OFF
Writing data to the CPU Unit's
data area
unit number)
Bit
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.
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: RXDU(255) was executed to write the data from
the buffer to a CPU Unit data area.
Reception Overflow Flag
0: The Unit has not received more than the speci-
fied number of bytes.
1: The Unit has received more than the specified
number of bytes.
0 1: The Unit received more data after data reception
was completed.
1 0: RXDU(255) was executed to write the data from
the buffer to a CPU Unit data area.
Reception Counter
Indicates the number of bytes received in hexadecimal,
between 0000 and 0100 hex (0 to 256 decimal).
End code or specified
number of bytes received.
Reception
processing
Instruction
execution
Section 3-23
Function
Write
processing
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