1020
Serial Communications Instructions Section 3-24
Example: Flag Operation The following diagram shows the operation of RXDU(255) and related flags.
Example: Receiving Data When CIO 000000 is ON, A20203 (the Communications Port Enabled Flag) is
ON, and CIO 155906 (the Reception Completed Flag for port 1) is OFF in the
following example, RXDU(255) reads the data received through serial port 1
of the Serial Communications Unit with unit number 2. (Logical communica-
tions port number 3 is used to receive the data from a general-purpose device
such as a bar-code reader.) The 10 bytes of received data are written to the
DM Area beginning at the rightmost byte of D00100.
End code or specified
number of bytes received.
Instruction
execution
ON
OFF
Communications Port
Enabled Flag
(A20200 to A20207 correspond to
communications ports 0 to 7.)
RXDU(255)
CPU Unit
Reception Completed Flag
(Bit 6 of n+9 or n+19,
n = CIO 1500 + 25 x unit number)
ON
OFF
Serial
Communications
Unit
Reception processing
Reception
processing
Writing data to the CPU Unit's
data area
Write
processing
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