Advantech PCI-1751U Manual de usuario descargar pdf (Pagina 32)

PCI-1751U User’s Manual 28

BCD Select binary or BCD counting

BCD Type

0 Binary counting 16-bits

1 Binary coded decimal (BCD) counting

If you set the module for binary counting, the count can be any number

from 0 up to 65535. If you set it for BCD (Binary Coded Decimal) count-

ing, the count can be any number from 0 to 9999.

If you set both SC1 and SC0 bits to 1, the counter control register is in

read-back command mode. The control register data format then

becomes:

BASE+27 8254 control, read-back mode

Bit D7D6D5D4D3D2D1D0

Val ue 1 1 CNT STA C2 C 1 C0 X

CNT = 0 Latch count of selected counter(s).

STA = 0 Latch status of selected counter(s).

C2, C1 & C0 Select counter for a read-back operation.

C2 = 1 select Counter 2

C1 = 1 select Counter 1

C0 = 1 select Counter 0

If you set both SC1 and SC0 to 1 and STA to 0, the register selected by

C2 to C0 contains a byte which shows the status of the counter. The data

format of the counter read/write register then becomes:

BASE+24/25/26 Status read-back mode

Bit D7 D6 D5 D4 D3 D2 D1 D0

Value OUT NC RW1 RW0 M2 M1 M0 BCD

OUT Current state of counter output

NC Null count is 1 when the last count written to the counter

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 38

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Advantech PCI-1751U Manual de usuario Pagina 32