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Intel® PXA255 Processor Developer’s Manual 6-37
Memory Controller
6.6.2 Synchronous Static Memory Mode Register Set
Configuration Register (SXMRS)
On power up, a MRS command that contains the default boot-up value is written to the external
memory if the system is configured to boot out of SMROM (see Section 6.10.2). Otherwise,
SXMRS, shown in Table 6-16, is used to issue an MRS command to SMROM. The value written
in this register is placed directly on address lines MA<24:10> during the MRS command. Writing
to this register triggers a two-stage MRS command that is sent to the external synchronous static
memory. The first state issues an MRS command to banks 0 and 1. The second stage issues an
MRS command to banks 2 and 3. The corresponding chip select values are only asserted if the
memory banks are enabled via the SXCNFG register and the memory type is configured as
SMROM.
To write a new MRS value to a synchronous static memory, first enable and configure the memory
via the SXCNFG register, then write the SXMRS register. This register is only used for the value
written during the MRS command. All values in the SXCNFG register must be programmed
correctly to ensure proper device operation (refer to the external memory chip product
documentation for proper MRS encoding). Information programmed in the SXCNFG[CL] and
Table 6-15. Synchronous Static Memory External to Internal Address Mapping Options
# Bits
Bank x
Row x
Col x
Data
External Address pins at SXMEM RAS Time
MA<24:10>
External Address pins at SXMEM CAS Time
MA<24:10>
24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
2x12x7x32
222120191817161514131211109 2221 0 8765432
2x12x7x16
21201918171615141312111098 2120 0 7654321
2x12x8x32
2322212019181716151413121110 2322 0 98765432
2x12x8x16 222120191817161514131211109 2221 0 87654321
2x12x9x32
2423222120191817161514131211 2423 0 1098765432
2x12x9x16
2322212019181716151413121110 2322 0 987654321
2x12x10x32
2524232221201918171615141312 2524 0111098765432
2x12x10x16
2423222120191817161514131211 2423 010987654321
2x13x7x32
232221201918171615141312111092322 0 8765432
2x13x7x16
22212019181716151413121110982221 0 7654321
2x13x8x32
2423222120191817161514131211102423 0 98765432
2x13x8x16
232221201918171615141312111092322 0 87654321
2x13x9x32
2524232221201918171615141312112524 0 1098765432
2x13x9x16 2423222120191817161514131211102423 0 987654321
2x13x10x16
2524232221201918171615141312112524 010987654321