Renesas SH7709S Manual de usuario descargar pdf (Pagina 27)

Rev. 1.0, 07/03, page 23 of 38

By writing data to address H'FFFFD000 + X or address H'FFFFE000 + X, the precharge all banks

command (PALL) is first issued at cycle TRp1, and a mode register write command is issued at

the following cycle TMw1. The address signals when a mode register write command is issued are

as follows.

32-bit bus width A15 to A9 0000100 (Burst read and single write)

A8 to A6 CAS latency

A5 0 (Burst type = sequential)

A4 to A2 000 (Burst length 1)

16-bit bus width A14 to A8 0000100 (Burst read and single write)

A7 to A5 CAS latency

A4 0 (Burst type = sequential)

A3 to A1 000 (Burst length 1)

Before specifying the mode register, 100 µs of idle time (differs depending on the memory

manufacturer) required for synchronous DRAM must be ensured after power-on. If the pulse

width of the reset signal is longer than this idle time, the mode register can be specified

immediately after power-on. In addition, dummy auto-refresh cycles must be executed for the

number of times specified by the manufacturer (normally 8 times) or more. Dummy auto-refresh

cycles are normally specified to be executed automatically during initializations after auto-refresh

setting. However, to ensure execution of the auto-refresh cycles, the time intervals between refresh

requests must be shortened while the dummy cycles are executed. Note that the auto-refresh cycles

must be executed in order to initialize the synchronous DRAM internal address counter because

the synchronous DRAM internal address counter cannot be initialized by a normal read or write

access.

2.2.3 HM5264165F-B60 (1 Mword × 16 bits × 4 banks)

Bus State Controller (BSC) Settings: When an SDRAM (HM5264165F-B60) is connected to

area 3 of the SH7727 via a 16-bit bus, the bus state controller (BSC) must be specified as

summarized below. Table 2.8 lists the BSC register settings.

Note that the interface between SDRAM and the SH7727 is performed with bus clock = 66 MHz,

CL = 2, TPC = 2, RCD = 2, TRWL = 1, and TRAS = 4.

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Renesas SH7709S Manual de usuario Pagina 27