SH7041A datasheet(496/923 Pages) RENESAS

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13.2.2

Timer Control/Status Register (TCSR)

The timer control/status register (TCSR) is an 8-bit read/write register. (The TCSR differs from

other registers in that it is more difficult to write to. See section 13.2.4, Register Access, for

details.) Its functions include selecting the timer mode and clock source.

Bits 7–5 are initialized to 000 by a power-on reset or in standby mode. Bits 2–0 are initialized to

000 by a power-on reset, but retain their values in the standby mode. These bits are not initialized

by a manual reset from an external source (

MRES), but are initialized by a manual reset from the

WDT.

Bit:

OVF

WT/

TME

—

CKS2

CKS1

CKS0

Initial value:

R/W:

R/(W)

R/W

• Bit 7—Overflow Flag (OVF): Indicates that the TCNT has overflowed from H'FF to H'00 in

the interval timer mode. It is not set in the watchdog timer mode.

Bit 7: OVF

Description

No overflow of TCNT in interval timer mode (initial value)

Cleared by reading OVF, then writing 0 in OVF

TCNT overflow in the interval timer mode

• Bit 6—Timer Mode Select (WT/IT): Selects whether to use the WDT as a watchdog timer or

interval timer. When the TCNT overflows, the WDT either generates an interval timer

interrupt (ITI) or generates a

WDTOVF signal, depending on the mode selected.

Bit 6: WT/

Description

Interval timer mode: interval timer interrupt request to the CPU when

TCNT overflows (initial value)

Watchdog timer mode:

WDTOVF signal output externally when TCNT

overflows. (Section 13.2.3, Reset Control/Status Register (RSTCSR),

describes in detail what happens when TCNT overflows in the watchdog

timer mode.)

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