CTP data: Determines the state of the general-purpose counter input pin (HCTR) when the general-purpose counter is
reset (CTE = 0).
CTP = 0: The general-purpose counter input pin is pulled down.
1: The general-purpose counter input pin is not pulled down, and the wait time is shortened by 1 to 2 ms.
IF CTP is to be set to 1, set CTP to 1 at least 4 ms before the counter is started by setting CTE to 1.
Leave CTP set to 0 if the counter will not be used.
IF counter operation
Reset the general-purpose counter in advance by setting CTE to 0 before starting the counter.
A general-purpose counter count operation is started by setting the CTE bit in the serial data to 1. The serial data takes
effect internally to the LC72147V when the CE pin input level is changed from high to low. The input to the HCTR pin
must be provided before the wait time has elapsed after CE was set low.
Next, the result of the general-purpose counter count after the measurement completes must be read out while CTE is still
set to 1. This is because the general-purpose counter is reset when CTE is set to 0.
Note that the signal input to the HCTR pin is first divided by 2 internally to the IC and then input to the general-purpose
counter. Therefore, the result of the general-purpose counter count is a value that corresponds to 1/2 of the frequency
actually input to the HCTR pin.
When used as an integrating counter
No. 6675-17/22
LC72147V
Frequency measurement mode
GT1
GT0
Measurement time
Wait time
CTP = 0
CTP = 1
0
0
4 ms
3 to 4 ms
0
1
8 ms
1 to 2 ms
1
0
32 ms
7 to 8 ms
1
1
64 ms
CE
HCTR
Frequency
measurement
time
Data with
CTE = 1
Wait time
Measurement time
Input signal
At least 70 mV rms
*
: When CTC = 0: 70 mV rms
When CTC = 1: 100 mV rms
Reset
Start
Restart
(Integrates)
Resets the general-purpose counter
Starts the general-purpose counter
Restarts the counter if set to 1 again.
CE
Internal data
latch (CTE)
GT
General-purpose
counter
End of the count operation
End of the count operation
end-UC
(DO)
1
*
CTE: 0
CTE = 0
*
CTE = 1
*
CTE = 1
*
In integrating count mode, the count value of the general-purpose counter is accumulated. Care must be taken to handle
counter overflow correctly. The count value will be in the range 0
H
to FFFFF
H
.
An integrating count operation is performed by sending the serial data (IN1) again with the CTE bit still set to 1. This
restarts the general-purpose counter measurement operation and adds the new counts to the previous counter value.