HD6417750RF240DV Datasheet, PDF(538/1132 Page) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

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HD6417750RF240DV Datasheet, PDF (538/1132 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

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Section 13 Bus State Controller (BSC)

SH7750, SH7750S, SH7750R Group

â¢ Self-Refreshing

Self-refresh mode is a kind of standby mode in which the refresh timing and refresh addresses

are generated within the synchronous DRAM. Self-refreshing is activated by setting both the

RMODE bit and the RFSH bit to 1. The self-refresh state is maintained while the CKE signal

is low. Synchronous DRAM cannot be accessed while in the self-refresh state. Self-refresh

mode is cleared by clearing the RMODE bit to 0. After self-refresh mode has been cleared,

command issuance is disabled for the number of cycles specified by bits TRC2âTRC0 in

MCR. Self-refresh timing is shown in figure 13.41. Settings must be made so that self-refresh

clearing and data retention are performed correctly, and auto-refreshing is performed at the

correct intervals. When self-refreshing is activated from the state in which auto-refreshing is

set, or when exiting standby mode other than through a power-on reset, auto-refreshing is

restarted if RFSH is set to 1 and RMODE is cleared to 0 when self-refresh mode is cleared. If

the transition from clearing of self-refresh mode to the start of auto-refreshing takes time, this

time should be taken into consideration when setting the initial value of RTCNT. Making the

RTCNT value 1 less than the RTCOR value will enable refreshing to be started immediately.

After self-refreshing has been set, the self-refresh state continues even if the chip standby state

is entered using this LSI's standby function, and is maintained even after recovery from

standby mode other than through a power-on reset.

In the case of a power-on reset, the bus state controller's registers are initialized, and therefore

the self-refresh state is cleared.

Self-refreshing is performed in normal operation, in sleep mode, in standby mode, and in the

case of a manual reset.

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R01UH0456EJ0702 Rev. 7.02

Sep 24, 2013

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