5 0
PCM-3718H/3718HG User's Manual
7.4 Counter Operations
Read/Write Operation
Before you write the initial count to each counter, you must first
specify the read/write operation type, operating mode and counter
type in the control byte and write the control byte to the control
register (BASE+15).
Since the control byte register and all three counter read/write
registers have separate addresses, and each control byte specifies the
counter it applies to (set by SC1 and SC0), no instructions on the
operating sequence are required. Any programming sequence
following the 8254 convention is acceptable.
There are three types of counter operation: read/load LSB, read/load
MSB and read/load LSB followed by MSB. It is important that you
make your read/write operations in pairs and keep track of the byte
order.
Counter Read-back Command
The 8254 counter read-back command lets you check the count
value, programmed mode and current states of the OUT pin and Null
Count flag of the selected counter(s). You write this command to the
control word register. Format is as shown at the beginning of the
chapter.
The read-back command can latch multiple counter output latches.
Simply set the CNT bit to 0 and select the desired counter(s). This
single command is functionally equivalent to multiple counter latch
commands, one for each counter latched.
The read-back command can also latch status information for selected
counter(s) by setting the STA bit to 0. The status must be latched to
be read; the status of a counter is accessed by a read from that counter.
For the counter status format please see the beginning of the chapter.
Counter Latch Operation
Users often want to read the value of a counter without disturbing the
count in progress. You can enable this function by latching the count
value for the specific counter and then reading the value.
Summary of Contents for 3718HG
Page 1: ...PCM 3718H 3718HG PC 104 12 bit DAS Module with Programmable Gain User s manual ...
Page 2: ......
Page 5: ...1 General Information CHAPT ER ...
Page 13: ...2 Installation CHAPT ER ...
Page 21: ...3 Signal Connections CHAPT ER ...
Page 26: ...22 PCM 3718H 3718HG User s Manual ...
Page 27: ...4 Register Structure and Format CHAPT ER ...
Page 38: ...34 PCM 3718H 3718HG User s Manual ...
Page 39: ...5 A D Conversion CHAPT ER ...
Page 45: ...6 Digital Input Output CHAPT ER ...
Page 47: ...7 Programmable Pacer CHAPT ER ...
Page 57: ...8 Direct Memory Access Operation CHAPT ER ...
Page 60: ...56 PCM 3718H 3718HG User s Manual ...
Page 61: ...9 Calibration CHAPT ER ...
Page 64: ...60 PCM 3718H 3718HG User s Manual ...