Cirrus-logic EP73xx Manual de usuario descargar pdf (Pagina 89)

EP7309/11/12 User’s Manual - DS508UM4 8-5

SRAM/Expansion Bus Controller

SQAEN[6]: Sequentialaccess enable. Settingthis bit willenable the sequential

accesses that are on a quad word boundary to take advantage of

faster access times from devices that support page mode. The

sequentialaccesseswillbe faultedafterfour words (toallow video

refresh cycles to occur), even if the access is part of a longer

sequential access. In addition, when this bit is not set, non-

sequential accesses will have a single idle cycle inserted at least

every four cycles so that the chip select is de-asserted periodically

between accesses for easier debug.

CLKENB[7]: Expansion clock enable. Setting this bit enables the

EXPCLK to be

active during accesses to the selected expansion device. This will

provide a timing reference for devices that need to extend bus

cycles using the

EXPRDY input. Back-to-back (but not necessarily

page mode) accesses will result in a continuous clock. This bit will

only affect

EXPCLK when the PLL is being used (i.e., in 73.728-

18.432 MHz mode.) When operating in 13 MHz mode, the

EXPCLK pinisaninput,soitisnotaffectedbythisregisterbit.To

saver power internally, it should always be set to zero when

operating at 13 MHz mode.

Memory Configuration Register 2 (MEMCFG2)

Address: 0x8000.01C0, Read / Write

Definition: See “Memory Configuration Register 1 (MEMCFG1)” details for

programming the remaining chip selects. Same programming

features and requirements apply.

Note: CS6 and CS7 are not configurable.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

nCS[7] Configuration nCS[6] Configuration

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

nCS[5] Configuration nCS[4] Configuration

1 2 ... 84 85 86 87 88 89 90 91 92 93 94 ... 157 158

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Cirrus-logic EP73xx Manual de usuario Pagina 89