SH7708 Datasheet, PDF (322/625 Pages) Renesas Technology Corp – SuperH™ RISC engine

1 1 . 3 TMU Operation
11.3.1 Overview
Each of the three channels has a 32-bit timer counter (TCNT) and a 32-bit timer constant register.
The TCNT counts down. The auto-reload function enables synchronized counting and counting by
external events. Channel 2 has an input capture function.
11.3.2 Basic Functions
Counter Operation: When the STR0–STR2 bits in the timer start register (TSTR) are set, the
corresponding timer counter (TCNT) starts counting. When a TCNT underflows (H'00000000 →
H'FFFFFFFF), the UNF flag of the corresponding timer control register (TCR) is set. At this
time, if the UNIE bit in TCR is 1, an interrupt request is sent to the CPU. Also at this time, the
value is copied from TCOR to TCNT and the down-count operation is continued.
The count operation is set as follows (figure 11.2):
1. Select the counter clock with the TPSC2–TPSC0 bits in the timer control register (TCR). If
the external clock is selected, set the TCLK pin to input mode with the TOCE bit in TOCR,
and select its edge with the CKEG1 and CKEG0 bits in TCR.
2. Use the UNIE bit in TCR to set whether to generate an interrupt when TCNT underflows.
3. When using the input capture function, set the ICPE bits in TCR, including the choice of
whether or not to use the interrupt function (channel 2 only).
4. Set a value in the timer constant register (TCOR) (the cycle is the set value plus 1).
5. Set the initial value in the timer counter (TCNT).
6. Set the STR bit in the timer start register (TSTR) to 1 to start operation.
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