NEC uPD78056Y - Manual (Page 234)

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CHAPTER 9 8-BIT TIMER/EVENT COUNTERS 1 AND 2
9.4.2 16-bit timer/event counter mode
When bit 2 (TMC12) of the 8-bit timer mode control register (TMC1) is set to 1, the 16-bit timer/event counter mode
is set.
In this mode, the count clock is set with bits 0 to 3 (TCL10 to TCL13) of timer clock select register 1 (TCL1), and
the overflow signal of 8-bit timer register 1 (TM1) becomes the count clock of 8-bit timer register 2 (TM2).
In this mode, enable/disable of the count operation is selected with bit 0 (TCE1) of TMC1.
(1) Operation as interval timer
The 8-bit timer/event counter operates as an interval timer that generates interrupt requests repeatedly at
intervals of the count value preset to 2-channel 8-bit compare registers (CR10 and CR20). When setting the
count value, set the value of the higher 8 bits to CR20 and the value of the lower 8 bits to CR10. For the count
value that can be set, refer to Table 9-9.
When 8-bit timer register 1 (TM1) and CR10 values match and 8-bit timer register 2 (TM2) and CR20 values
match, counting continues with the TM1 and TM2 values cleared to 0 and the interrupt request signal (INTTM2)
is generated. For the timing of interval timer operation, refer to Figure 9-11.
The count clock is selected with bits 0 to 3 (TCL10 to TCL13) of timer clock select register 1 (TCL1), and
the overflow signal of TM1 becomes the count clock of TM2.
Figure 9-11. Interval Timer Operation Timing
Remark Interval time = (N + 1)
×
t : N = 0000H to FFFFH
Caution Even if the 16-bit timer/event counter mode is used, when the TM1 count value matches the
CR10 value, interrupt request (INTTM1) is generated and the F/F of 8-bit timer/event counter
output control circuit 1 is inverted. Thus, when using 8-bit timer/event counter as 16-bit
interval timer, set the INTTM1 mask flag TMMK1 to 1 to disable INTTM1 acknowledgment.
When reading the 16-bit timer register (TMS) count value, use the 16-bit memory manipulation
instruction.
Count Clock
TMS (TM1, TM2) Count Value
CR10, CR20
INTTM2
TO2
Interval Time Interval Time Interval Time
Interrupt Request Acknowledge Interrupt Request Acknowledge
N N N N
Count Start Clear Clear
0000 0001 N 0000 0001 N 0000 0001 N
t