STATIC MEMORY CONTROLLER
S3C2416X RISC MICROPROCESSOR
5-8
3.4 ASYNCHRONOUS
WRITE
You can program the delay between the assertion of the chip select and the write enable from 0-15 cycles using
the WSTWEN bits of the Bank Write Enable Assertion Delay Control Register, SMBWSTWENRx. This reduces
the power consumption for memories. The write enable is asserted on the rising edge of nSMMEMCLK, half a
clock after the assertion of chip select.
For most asynchronous memory devices an SMMEMCLK cycle is required before the assertion of nWE otherwise
there is the hazard that nCS changes after nWE. You can add extra cycles before nWE is asserted using the
WSTWEN bits in the Bank Write Enable Assertion Delay Control Registers. For example, setting
WSTWR=WSTWEN=1 extends the transfer by one cycle and delays the assertion of nWE by one cycle.
The Write enable is always deasserted half a cycle before the chip select, at the end of the transfer. nSMBLS has
the same timing as nSMWEN for writes to 8-bit devices that use the byte lane selects instead of the write enables.
The WSTWEN programmed value must be equal to, or less than the WSTWR programmed value otherwise an
invalid access sequence is generated. The access is timed by the WSTWR value and not by the WSTWEN value.
In the External Wait enabled mode, the timing of the transfer (controlled by SMWAIT) is not known. WSTWEN still
delays the assertion of nSMWEN. nSMWEN is delayed more by the external wait signal if it has not been
asserted when SMWAIT is asserted.
You might require the SMADDRVALID signal for synchronous static memory devices when you use it in
asynchronous mode. You can disable it using the AddrValidWriteEn bit in the SMBCRx Register. This bit defaults
to being set(enable). You can then clear it if you do not require it. When you disable it, the signal is driven HIGH
continuously.
Figure 5-8 shows a single external memory write transfer with two write enable delay states, WSTEN=2, and two
wait states, WSTWR=2. A single AHB wait state is inserted.
SMCLK
ADDR
DATA(OUT)
Asynchronous Write
nCS
SMAVD
nWE
A
D(A)
WSTWR=2
WSTWEN=2
Figure 5-8. External Memory Two Write Enable Delay State Write
Содержание S3C2416
Страница 33: ...S3C2416X RISC MICROPROCESSOR PRODUCT OVERVIEW 1 5 3 BLOCK DIAGRAM Figure 1 1 S3C2416X Block Diagram ...
Страница 38: ...PRODUCT OVERVIEW S3C2416X RISC MICROPROCESSOR 1 10 153 AIN 1 U14 195 EINT 10 GPG2 K15 237 SDATA 14 C18 ...
Страница 122: ...BUS MATRIX EBI S3C2416X RISC MICROPROCESSOR 3 4 NOTES ...
Страница 204: ...DMA CONTROLLER S3C2416X RISC MICROPROCESSOR 8 18 NOTES ...
Страница 284: ...WATCHDOG TIMER S3C2416X RISC MICROPROCESSOR 11 6 NOTES ...
Страница 320: ...REAL TIME CLOCK S3C2416X RISC MICROPROCESSOR 13 16 NOTES ...
Страница 344: ...UART S3C2416X RISC MICROPROCESSOR 14 24 NOTES ...
Страница 380: ...USB2 0 DEVICE S3C2416X RISC MICROPROCESSOR 16 34 NOTES ...
Страница 432: ...2D S3C2416X RISC MICROPROCESSOR 18 38 NOTES ...
Страница 446: ...HS_SPI CONTROLLER S3C2416X RISC MICROPROCESSOR 19 14 NOTES ...
Страница 455: ...S3C2416X RISC MICROPROCESSOR HSMMC CONTROLLER 20 9 4 9 SD COMMAND ISSUE SEQUENCE Figure 20 9 Timeout Setting Sequence ...
Страница 604: ...S3C2416X RISC MICROPROCESSOR S3C2416X RISC MICROPROCESSOR 23 22 NOTES ...
Страница 638: ...PCM AUDIO INTERFACE S3C2416X RISC MICROPROCESSOR 25 18 NOTES ...
Страница 653: ...S3C2416X RISC MICROPROCESSOR ELECTRICAL DATA 26 15 Figure 26 14 SDRAM READ WRITE Timing Trp 2 Trcd 2 Tcl 2 DW 16 bit ...
Страница 670: ...ELECTRICAL DATA S3C2416X RISC MICROPROCESSOR 26 32 NOTES ...
Страница 672: ...MECHANICAL DATA S3C2416X RISC MICROPROCESSOR 30 2 Figure 27 2 330 FBGA 1414 Package Dimension 2 Bottom View ...