Measurement-computing CIO-DAS-TEMP Bedienungsanleitung PDF herunterladen (Seite 14)

First, program the 82C54 control register for CTR 1 to produce a single pulse for the duration of the

count period. Next, load an initial value equal to the period for which counts from the V/F converter will

be totaled See the previous explanation of initial count values for information on what value to load into

this counter. It works as a down-counter, the only choice available.

BASE + 1 Read - Counter 1 Current Count Register of the 82C54

Data 0Data 1Data 2Data 3Data 4Data 5Data 6Data 7

01234567

Will return current count.

BASE + 2 Write - Counter 2 Load Register of the 82C54

Data 0Data 1Data 2Data 3Data 4Data 5Data 6Data 7

01234567

This counter is used to sequence through multiple channels when more than one channel is read. First,

program the 82C54 control register for CTR 2 to function as a rate generator. The register at Base + 5

sets the input (prescaler) frequency for this counter.

Next, load an initial value equal to the number of clock periods between channel readings

BASE + 2 Read - Counter 2 Current Count Register of the 82C54

Data 0Data 1Data 2Data 3Data 4Data 5Data 6Data 7

01234567

Will return current count.

BASE + 3 Write - Control Register of the 82C54

BCDM0M1M2RW0RW1SC0SC1

01234567

The 82C54 counter is described in g reat detail in the Harris or Instel 82C54 data sheet. A brief

description of the control bits follows.

SC1

SC0 Function

0 0 Select counter 0

0 1 Select counter 1

1 0 Select counter 2

1 1 Read Command

RW1

RW0 Function

0 0 Counter latch

0 1 Read/Write least significant byte of selected counter

1 0 Read/Write most significant byte of selected counter

1 1 Read/Write least significant byte then most significant byte

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 20

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Measurement-computing CIO-DAS-TEMP Bedienungsanleitung Seite 14