10: U
SER
C
OMMUNICATION
I
NSTRUCTIONS
FC5A M
ICRO
S
MART
U
SER
’
S
M
ANUAL
FC9Y-B1268
10-15
RXD (Receive)
When input is on, data from an RS232C remote terminal received by port 1
through port 7 is converted and stored in data registers according to the
receive format designated by S1.
RXD2 to RXD7 can be used to communicate with an RS485 remote terminal on
port 2 to port 7.
RXD3 through RXD7 are available on upgraded CPU modules with system pro-
gram version 110 or higher. For details about expansion RS232C/RS485 com-
munication on port 3 to port 7, see page 25-1 (Advanced Vol.).
S1
*****
D1
*****
D2
*****
RXD
*
Applicable CPU Modules
FC5A-C10R2/C/D
FC5A-C16R2/C/D
FC5A-C24R2D
FC5A-C24R2/C
FC5A-D16RK1/RS1
FC5A-D32K3/S3
FC5A-D12K1E/S1E
RXD1-RXD2
RXD1-RXD2
RXD1-RXD5
RXD1-RXD7
RXD1-RXD7
RXD2-RXD7
Valid Devices
Device
Function
I
Q
M
R
T
C
D
Constant
Repeat
S1 (Source 1)
Receive format
— — — — — —
X
X
—
D1 (Destination 1)
Receive completion output
—
X
— — — —
—
—
D2 (Destination 2)
Receive status
— — — — — —
X
—
—
For the valid device address range, see pages 6-1 and 6-2.
Internal relays M0 through M2557 can be designated as D1. Special internal relays cannot be designated as D1.
Receive format designated by device S1 can be a maximum of 200 bytes.
When data receive is complete, an output or internal relay, designated by device D1, is turned on.
Destination 2 occupies two consecutive data registers starting with the device designated by D2. The receive status data register, D0-
D1998, D2000-D7998, or D10000-D49998, stores the status of data receive and error code. The next data register stores the byte count
of received data. The same data registers can not be used as transmit status registers for TXD1 through TXD7 instructions and receive
status registers for RXD1 through RXD7 instructions.
The RXD instructions cannot be used in an interrupt program. If used, a user program execution error will result, turning on special
internal relay M8004 and the ERR LED on the CPU module.
Precautions for Programming the RXD Instruction
The MicroSmart can execute a maximum of five instructions each of RXD1 through RXD7 that have a start delimiter at the same time.
If a start delimiter is not programmed in RXD1 through RXD7 instructions, the MicroSmart can execute only one instruction each of
RXD1 through RXD7 at a time. If the start input for a RXD1 through RXD7 instruction is turned on while another RXD1 through RXD7
instruction without a start delimiter is executed, a user communication error occurs.
Since RXD instructions are executed in each scan while input is on, a pulse input from a SOTU or SOTD instruction should be used as
required.
Once the input to the RXD instruction is turned on, the RXD is activated and ready for receiving incoming communication even after
the input is turned off. When the RXD completes data receiving, the RXD is deactivated if the input to the RXD is off. Or, if the input is
on, the RXD is made ready for receiving another communication. Special internal relays are available to deactivate all RXD instruc-
tions waiting for incoming communication. For user communication receive instruction cancel flags, see page 10-28.
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