S29WS-NL Datasheet, PDF (42/99 Pages) SPANSION – 256/128/64 MEGABIT CMOS 1.8 VOLT ONLY SIMULTANEOUS READ/WRITE BURST MODE FLASH MEMORY

Advance Information
If the system asserts V_HH on this input, the device automatically enters the aforementioned Un-
lock Bypass mode and uses the higher voltage on the input to reduce the time required for
program and erase operations. The system can then use the Write Buffer Load command se-
quence provided by the Unlock Bypass mode. Note that if a “Write-to-Buffer-Abort Reset” is
required while in Unlock Bypass mode, the full 3-cycle RESET command sequence must be used
to reset the device. Removing V_HH from the ACC input, upon completion of the embedded pro-
gram or erase operation, returns the device to normal operation.
„ Sectors must be unlocked prior to raising ACC to V_HH.
„ The ACC pin must not be at V_HH for operations other than accelerated programming and
accelerated chip erase, or device damage may result.
„ The ACC pin must not be left floating or unconnected; inconsistent behavior of the device
may result.
„ ACC locks all sector if set to V_IL; ACC should be set to V_IH for all other conditions.
7.5.8 Unlock Bypass
The device features an Unlock Bypass mode to facilitate faster word programming. Once the de-
vice enters the Unlock Bypass mode, only two write cycles are required to program data, instead
of the normal four cycles.
This mode dispenses with the initial two unlock cycles required in the standard program command
sequence, resulting in faster total programming time. The “Command Definition Summary” sec-
tion shows the requirements for the unlock bypass command sequences.
During the unlock bypass mode, only the Read, Unlock Bypass Program and Unlock Bypass Reset
commands are valid. To exit the unlock bypass mode, the system must issue the two-cycle unlock
bypass reset command sequence. The first cycle must contain the bank address and the data 90h.
The second cycle need only contain the data 00h. The bank then returns to the read mode.
Software Functions and Sample Code
The following are C source code examples of using the unlock bypass entry, program, and exit
functions. Refer to the Spansion Low Level Driver User’s Guide (available soon on www.amd.com
and www.fujitsu.com) for general information on Spansion Flash memory software development
guidelines.
Table 7.20. Unlock Bypass Entry
(LLD Function = lld_UnlockBypassEntryCmd)
Cycle
1
2
3
Description
Unlock
Unlock
Entry Command
Operation
Write
Write
Write
Byte Address
Base + AAAh
Base + 554h
Base + AAAh
Word Address
Base + 555h
Base + 2AAh
Base + 555h
Data
00AAh
0055h
0020h
/* Example: Unlock Bypass Entry Command */
*( (UINT16 *)bank_addr + 0x555 ) = 0x00AA; /* write unlock cycle 1
*/
*( (UINT16 *)bank_addr + 0x2AA ) = 0x0055; /* write unlock cycle 2
*/
*( (UINT16 *)bank_addr + 0x555 ) = 0x0020; /* write unlock bypass command
*/
/* At this point, programming only takes two write cycles. */
/* Once you enter Unlock Bypass Mode, do a series of like */
/* operations (programming or sector erase) and then exit */
/* Unlock Bypass Mode before beginning a different type of */
/* operations.
*/
Table 7.21. Unlock Bypass Program
(LLD Function = lld_UnlockBypassProgramCmd)
Cycle
1
Description
Program Setup Command
Operation
Write
Byte Address
Base + xxxh
Word Address
Base +xxxh
Data
00A0h
40
S29WS-N_00_G0 January 25, 2005