HD6433713 datasheet(152/324 Pages) RENESAS

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Timer counter A (TCA)

TCA is an 8-bit read-only up-counter, which is incremented by internal clock input. The clock

source for input to this counter is selected by bits TMA3 to TMA0 in timer mode register A

(TMA). The TCA value can be read by the CPU at any time.

TCA is cleared by setting bits TMA3 and TMA2 of TMA to 1.

When TCA overflows, the IRRTA bit in interrupt request register 2 (IRR2) is set to 1.

Upon reset, TCA is initialized to H'00.

8.2.3 Timer Operation

Timer A is an 8-bit timer which can be used either as an interval timer or, if a 32.768 kHz crystal

oscillator is connected, as a real-time clock time base.

Interval timer operation

When bit TMA3 in timer mode register A (TMA) is cleared to 0, timer A functions as an 8-bit

interval timer.

Upon reset, TCA is cleared to H'00 and bit TMA3 is cleared to 0, so up-counting and interval

timing resume immediately after the reset. The clock input to timer A is selected by bits

TMA2 to TMA0 in TMA; any of eight internal clock signals output by prescaler S can be

selected.

After the count value in TCA reaches H'FF, the next clock signal input causes timer A to

overflow, setting bit IRRTA to 1 in interrupt request register 2 (IRR2). If IENTA = 1 in

interrupt enable register 2 (IENR2), a CPU interrupt is requested.*

At overflow, TCA returns to H'00 and starts counting up again. In this mode timer A

functions as an interval timer that generates an overflow output at intervals of 256 input clock

pulses.

Note: * For details on interrupts, see 3.2.2, Interrupts.

Bit

Initial value

Read/Write

TCA7

TCA6

TCA5

TCA4

TCA3

TCA0

TCA2

TCA1

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HD6433713 Datasheet(PDF) 152 Page - Renesas Technology Corp