CHAPTER 9 8-BIT TIMERS 30 AND 40
User’s Manual U14826EJ5V0UD
110
The operation of the carrier generator is as follows.
<1> When the count value of TM40 matches the value set in CR40, an interrupt request signal (INTTM40) is
generated and output of timer 40 is inverted, which makes the compare register switch from CR40 to
CRH40.
<2> After that, when the count value of TM40 matches the value set in CRH40, an interrupt request signal
(INTTM40) is generated and output of timer 40 is inverted again, which makes the compare register switch
from CRH40 to CR40.
<3> The carrier clock is generated by repeating <1> and <2> above.
<4> When the count value of TM30 matches the value set in CR30, an interrupt request signal (INTTM30) is
generated. The rising edge of INTTM30 is the data reload signal of NRZB40 and is transferred to NRZ40.
<5> When NRZ40 is 1, a carrier clock is output from TMO pin.
Cautions 1. TCA40 cannot be set with a 1-bit memory manipulation instruction. Be sure to use an 8-bit
memory manipulation instruction to set TCA40.
2. The NRZ40 flag can be written only when carrier generator output is stopped (TOE40 = 0).
The data cannot be overwritten when TOE40 = 1.
3. When the carrier generator is stopped once and then started again, NRZB40 does not hold
the previous data. Re-set data to NRZB40. At this time, a 1-bit memory manipulation
instruction must not be used. Be sure to use an 8-bit memory manipulation instruction.
4. To enable operation in the carrier generator mode, set a value to the compare registers
(CR30, CR40, and CRH40), and input the necessary value to the NRZB40 and NRZ40 flags in
advance. Otherwise, the signal of the timer match circuit will become unstable and the
NRZ40 flag will be undefined.
5. Note that the
µ
PD78E9860 and 78E9861 have the following restrictions (which do not apply to
the mask ROM version and the
µ
PD78E9860A and 78E9861A).
(a) While INTTM30 (interrupt generated by the match signal of timer 30) is being output,
accessing TCA40 is prohibited.
(b) Accessing TCA40 is prohibited while 8-bit timer/counter 30 (TM30) is 00H.
To access TCA40 while TM30 = 00H, wait for more than half a period of the TM30 count
clock and then rewrite TCA40.
Содержание PD789860
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