Motorola MCF5281, MCF5282 user manual Initialization Sequence, Self-Refresh Operation

Models: MCF5282 MCF5281

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SDRAM Controller Operation

CLKOUT

SRAS

 

 

 

 

 

 

 

 

 

tRCD = 2

 

 

SCAS

 

 

 

DRAMW

SDRAM_CS[0] or [1]

SCKE (DCR[COC] = 0)

PALL

SELF

SELFX

Self-

Refresh

Active

tRC = 6

First

Possible

ACTV

Figure 15-9. Self-Refresh Operation

15.2.4 Initialization Sequence

Synchronous DRAMs have a prescribed initialization sequence. The DRAM controller supports this sequence with the following procedure:

1.SDRAM control signals are reset to idle state. Wait the prescribed period after reset before any action is taken on the SDRAMs. This is normally around 100 µs.

2.Initialize the DCR, DACR, and DMR in their operational configuration. Do not yet enable PALL or REF commands.

3.Issue a PALL command to the SDRAMs by setting DACR[IP] and accessing a SDRAM location. Wait the time (determined by tRP) before any other execution.

4.Enable refresh (set DACR[RE]) and wait for at least 8 refreshes to occur.

5.Before issuing the MRS command, determine if the DMR mask bits need to be modified to allow the MRS to execute properly

6.Issue the MRS command by setting DACR[IMRS] and accessing a location in the SDRAM. Note that mode register settings are driven on the SDRAM address bus, so care must be taken to change DMR[BAM] if the mode register configuration does not fall in the address range determined by the address mask bits. After the mode register is set, DMR mask bits can be restored to their desired configuration.

MOTOROLA

Chapter 15. Synchronous DRAM Controller Module

15-17

Page 331
Image 331
Motorola MCF5281, MCF5282 user manual Initialization Sequence, Self-Refresh Operation