Memory Controller

Table 6-42. Memory Controller Pin Reset Values

Pin Name

PXA255 Processor Reset Value

 

 

SDCLK [2:0]

000

 

 

SDCKE <1>

00

 

 

SDCKE <0>

1 if BOOT_SEL = Synchronous Memory

 

 

DQM [3:0]

0000

 

 

nSDCS [3:0]

1111

 

 

nWE

1

 

 

nSDRAS

1

 

 

nSDCAS

1

 

 

nOE

1

 

 

MA [25:0]

0x0000000h

 

 

RDnWR

0

 

 

MD [31:0]

0x00000000h

 

 

nCS <0>

1

 

 

nCS <5:1>

GPIO Input

 

 

nPIOIR

GPIO Input

 

 

nPIOIW

GPIO Input

 

 

nPOE

GPIO Input

 

 

nPWE

GPIO Input

 

 

In sleep mode, the memory pins and controller are in the same state as they are after a hardware reset, except that the GPIO signals are driven high. If SDRAMs are in self-refresh, they are held there by setting SDCKE<1> to a 0.

6.11Hardware, Watchdog, or Sleep Reset Operation

Software performs the following procedures when the processor comes out of a reset:

1.After hardware reset, complete a power-on wait period of 200 ∝s, which allows the internal clocks that generate SDCLK to stabilize. Enable MDREFR:K0RUN and E0PIN for Synchronous Static memory. When MDREFR is written, a refresh interval value (MDREFR:DRI) must also be written. The following writes are allowed:

a.Write MSC0, MSC1, MSC2

b.Write MECR, MCMEM0, MCMEM1, MCATT0, MCATT1, MCIO0, MCIO1

c.Write MDREFR:K0RUN and MDREFR:E0PIN. Configure MDREFR:K0DB2. Retain the current values of MDREFR:APD and MDREFR:SLFRSH. MDREFR:DRI must contain a valid value. Deassert MDREFR:KxFREE.

2.In systems that contain Synchronous Static memory, write to the SXCNFG to configure all appropriate bits, including the enable bits. Software must perform a sequence that involves a subsequent write to SXCNFG to change the RAS latencies. While any SMROM banks are

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Hardware, Watchdog, or Sleep Reset Operation, Memory Controller Pin Reset Values