HD6433713 datasheet(175/324 Pages) RENESAS

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8.6.3 Timer Operation

Timer E is an 8-bit up-counter that is incremented each time a clock pulse is input. It functions as

an interval or auto-reload timer. It can also output a square wave having a 50% duty cycle. Each

of these operation modes is explained below.

Interval timer operation

When bit TME7 in timer mode register E (TME) is cleared to 0, timer E functions as an 8-bit

interval timer.

Upon reset, timer counter E (TCE) is reset to H'00 and bit TME7 is cleared to 0, so up-

counting and interval timing resume immediately after the reset. The clock input to timer E is

selected from eight internal clock signals output by prescaler S. The selection is made by bits

TME2 to TME0 in TME.

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

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

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

At overflow, TCE returns to H'00, and starts counting up again.

During interval timer operation (TME7 = 0), when a value is set in timer load register E

(TLE), the same value is set in TCE.

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

Auto-reload timer operation

Setting bit TME7 in TME to 1 causes timer E to function as an 8-bit auto-reload timer. When

a reload value is set in TLE, the same value is loaded into TCE, becoming the value from

which TCE starts its count.

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

overflow. The TLE value is then loaded into TCE, and the count continues from that value.

The overflow period can be set within a range from 1 to 256 input clocks, depending on the

TLE value.

The clock sources and interrupts in auto-reload mode are the same as for interval mode.

In auto-reload mode (bit TME7 = 1), setting a new TLE value also initializes TCE.

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HD6433713 Datasheet(PDF) 175 Page - Renesas Technology Corp