SH7708 datasheet(228/633 Pages) RENESAS

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and pseudo-SRAM, specifies address multiplexing, and controls refresh. This enables direct

connection of DRAM, synchronous DRAM and pseudo-SRAM without external circuits.

MCR is initialized to H'0000 by a power-on reset, but is not initialized by a manual reset or in

standby mode. Bits TPC1–TPC0, RCD1–RCD0, TRWL1–TRWL0, TRAS1–TRAS0, BE, SZ,

AMX1–AMX0, and EDOMODE are written to in the initialization after a power-on reset and are

not then modified again. When RFSH and RMODE are written to, write the same values to the

other bits. When using DRAM, pseudo-SRAM, and synchronous DRAM, do not access areas 2

and 3 until this register is initialized.

Bit:

Bit name:

TPC1

TPC0

RCD1

RCD0

TRWL1

TRWL0

TRAS1

TRAS0

000

R/W:

R/W

Bit:

Bit name:

—

AMX1

AMX0

RFSH

RMODE

EDO

MODE

Initial value:

R/W:

R/W

Bits 15 and 14—RAS Precharge Time (TPC1, TPC0): When DRAM interface is selected as

connected memory, the TPC bits set the minimum number of cycles until the next

RAS assertion

after

RAS negation. When synchronous DRAM interface is selected, they set the minimum

number of cycles until output of the next bank-active command after precharge. When pseudo-

SRAM interface is selected, they set the minimum number of cycles until the next

CE assertion

after

CE negation.

Description

Bit 15: TPC1

Bit 14: TPC0

Normally

Immediately after Self-Refresh

1 cycle (Initial value)

2 cycles (Initial value)

2 cycles

5 cycles

3 cycles

8 cycles

4 cycles

11 cycles

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