SH7721 datasheet(625/1524 Pages) RENESAS

Part #	SH7721

Description	Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

PDF	1524 Pages

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Manufacturer	RENESAS [Renesas Technology Corp]

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Section 17 Realtime Clock (RTC)

Rev. 3.00 Jan. 18, 2008 Page 563 of 1458

REJ09B0033-0300

17.3.1

64-Hz Counter (R64CNT)

R64CNT indicates the state of the divider circuit between 64 Hz and 1 Hz.

Reading this register, when carry from 128-Hz divider stage is generated, sets the CF bit in the

RTC control register 1 (RCR1) to 1 so that the carrying and reading 64 Hz counter are performed

at the same time is indicated. In this case, the R64CNT should be read again after writing 0 to the

CF bit in RCR1 since the read value is not valid.

After the RESET bit or ADJ bit in the RTC control register 2 (RCR2) is set to 1, the RTC divider

circuit is initialized and R64CNT is initialized to H'00.

R64CNT is not initialized by a power-on reset or manual reset, or in standby mode.

Bit

Bit Name

Initial Value

R/W

Description



Reserved

This bit is always read as 0. Writing has no effect.

1 Hz

Undefined

2 Hz

Undefined

4 Hz

Undefined

8 Hz

Undefined

16 Hz

Undefined

32 Hz

Undefined

64 Hz

Undefined

Indicate the state of the divider circuit between

64 Hz and 1 Hz.

SH7721 Datasheet(PDF) 625 Page - Renesas Technology Corp