UPD17073 NEC, UPD17073 Datasheet - Page 153

• Manufacturer Part Number: UPD17073
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER WITH HARDWARE FOR DIGITAL TUNING SYSTEM
• Manufacturer: NEC

16.4.2
the P0D2/AMIFC or P0D3/FMIFC/AMIFC pin to be used for the IF counter has been executed, until the counter is
actually started.
selected for the IF counter function, as described in 16.4.1.
16.4.3
(1) Gate time error
(2) Count error
A program example of the IF counter is shown below.
As shown in this example, make sure that a wait time of a certain length elapses after an instruction that specifies
This is because the internal AC amplifier is not ready for normal operation immediately after the pin has been
Example To count frequency of P0D3/FMIFC/AMIFC pin (FMIF count mode) (gate time: 8 ms)
The IF counter has a gate time error and count error, as described in (1) and (2) below.
LOOP:
READ:
The gate time of the IF counter is created by dividing the 75-kHz system clock frequency.
Therefore, if this frequency has an error of “+x” ppm, the gate time accordingly has an error of “-x” ppm.
The IF counter counts frequency at the rising edge of the input signal.
Therefore, if a high-level signal is input to the pin when the gate is opened, one extra pulse is counted.
However, this extra pulse may not be counted, depending on the status of the pin, when the gate is closed.
Therefore, the count error is “+1, -0”.
Program example of IF counter
Error of IF counter
BANK1
INITFLG
SET1
SET1
SKT1
BR
BR
GET
Processing A
Wait
IFCMD1, NOT IFCMD0, IFCCK1, NOT IFCCK0
IFCRES
IFCSTRT ; Starts IF count
IFCG
READ
LOOP
DBF, IFC ; Reads value of IF counter data register to data buffer
; Selects FMIFC pin (FMIF count mode) and sets gate time to 8 ms
; Internal AC amplifier stabilization time
; Resets IF counter
; Detects opening/closing of gate
; Branches to READ: if gate is closed
; Do not read data of IF counter with this processing A.
PD17072,17073
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