PD17012_15 Datasheet, PDF (132/320 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DIGITAL TUNING SYSTEM HARDWARE

µPD17012, 17P012
12.3.4 Error of basic timer 1
As described in 12.3.3, the interrupt generated by basic timer 1 is acknowledged each time the basic timer 1
interrupt pulse falls, if the EI instruction has been executed, and if the interrupt has been enabled.
Therefore, an error of basic timer 1 occurs only when any of the following operations (1) to (3) is performed:
(1) When the first interrupt after the basic timer 1 interrupt has been enabled has been acknowledged
(2) When the time interval at which the IRQBTM1 flag is to be set is changed, i.e., when the first interrupt is
acknowledged after the interrupt pulse has been changed
(3) When data has been written to the IRQBTM1 flag
Figure 12-12 shows an error in each of the above operations.
Figure 12-12. Error of Basic Timer 1 (1/2)
(a) When interrupt by basic timer 1 is enabled
Basic timer 1 ^H
interrupt pulse _L
1
IRQBTM1 flag ₀
IPBTM1 flag ¹
0
EI
INTE FF
DI
tSET
EI
EI
Interrupt pending
<1><2>
SET1 IPBTM1
interrupt
acknowledged
EI
<3>
Interrupt
acknowledged
Interrupt
acknowledged
At point <1> in the above figure, the interrupt by basic timer 1 is acknowledged as soon as the interrupt
is enabled.
At this time, the error is –tSET.
If an interrupt is enabled by the “EI” instruction at the next point <2>, the interrupt occurs at the falling edge
of the basic timer 1 interrupt pulse.
At this time, the error is:
–tSET < error < 0
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Data Sheet U10101EJ4V0DS