IDEC MICROSmart FC6A Series, Руководство по программированию на языке лестничных схем

Страница: 464 / 604

23: F
ILE
D
ATA
P
ROCESSING
I
NSTRUCTIONS
23-2 FC6A S
ERIES
MICROS
MART
L
ADDER
P
ROGRAMMING
M
ANUAL
FC9Y-B1726
Destination Device D1 (FIFO Data File)
FIFO data files are initialized when corresponding FIFOF instructions are executed. FIFO data file is placed in the area starting with
the device designated by D1 and occupies as many as S1
×
S2+2 data registers. The size of each record is equal to S1. S1-1 records
of data can be stored in an FIFO data file using FIEX instructions. The stored data can be retrieved from the FIFO data file using
FOEX instructions.
Destination Device D2 (FIFO Status Output)
When FIEX or FOEX instructions are executed, the following internal relays are turned on or off according to the execution status.
Note: The FIFOF instruction 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 FC6A Series MICROSmart. For
details about the user program execution errors, see "User Program Execution Errors" on page 3-10.
Device Function Description
D1+0 FI pointer
The FI pointer indicates the position to store new data into the FIFO data file. When an
FIEX instruction is executed, the new data in data registers starting with the device
designated by S1 of the FIEX instruction is stored at the position indicated by the FI
pointer, and the FI pointer is incremented by 1 to indicate the position to store the next
data.
When the FI pointer indicates the last record of the FIFO data file, and an FIEX
instruction is executed, the FI pointer will return to 0.
D1+1 FO pointer
The FO pointer indicates the position to retrieve the stored data from the FIFO data
file. When an FOEX instruction is executed, the data at the position indicated by the
FIFO pointer is retrieved and stored to the data registers starting with the device
designated by D1 of the FOEX instruction, and the FO pointer is incremented by 1 to
indicate the position to retrieve the next data.
When the FO pointer indicates the last record of the FIFO data file, and an FOEX
instruction is executed, the FO pointer will return to 0.
D1+2
Record 0 The first record to store the data. ...
D1+(S1+1)
D1+(S1+2)
Record 1 The second record to store the data. ...
D1+(S1
× 2+1)
D1+(S1 × (S2–1)+2)
Record S2–1 The last record to store the data. ...
D1+(S1
× S2+1)
D2 Assignments Function Description
D2+0 Data file full output
When the value stored in the FI pointer (D1+0) is equal to the value stored in the FO
pointer (D1+1) – 1, the FIFO data file is full, and no more data can be stored. If an FIEX
instruction is executed when the FIFO data file is full, no operation is executed, and the
data file full output (D2+0) will be turned on.
D2+1 Data file empty output
When the value stored in the FI pointer (D1+0) is equal to the value stored in the FO
pointer (D1+1), the FIFO data file is empty. If an FOEX instruction is executed when the
FIFO data file is empty, no operation is executed, and the data file empty output (D2+1)
will be turned on.
D2+2
Pointer out of range
output
The value stored in the FI or FO pointer can be 0 through S2–1. When an FIEX or FOEX
instruction is executed while the FI or FO pointer value exceeds the valid range, no
operation is executed, and the pointer out of range output (D2+2) will be turned on.