Document Number: 001-98285 Rev. *R
Page 24 of 108
S29GL01GS/S29GL512S
S29GL256S/S29GL128S
5.4.1.2
Write Buffer Programming
A write buffer is used to program data within a 512-byte address range aligned on a 512-byte boundary (Line). Thus, a full Write
Buffer Programming operation must be aligned on a Line boundary. Programming operations of less than a full 512 bytes may start
on any word boundary but may not cross a Line boundary. At the start of a Write Buffer programming operation all bit locations in the
buffer are all 1’s (FFFFh words) thus any locations not loaded will retain the existing data. See
for
information on address map.
Write Buffer Programming allows up to 512 bytes to be programmed in one operation. It is possible to program from 1 bit up to 512
bytes in each Write Buffer Programming operation. It is recommended that a multiple of Pages be written and each Page written only
once. For the very best performance, programming should be done in full Lines of 512 bytes aligned on 512-byte boundaries.
Write Buffer Programming is supported only in the main flash array or the SSR ASO.
The Write Buffer Programming operation is initiated by first writing two unlock cycles. This is followed by a third write cycle of the
Write to Buffer command with the Sector Address (SA), in which programming is to occur. Next, the system writes the number of
word locations minus 1. This tells the device how many write buffer addresses are loaded with data and therefore when to expect the
Program Buffer to flash confirm command. The Sector Address must match in the Write to Buffer command and the Write Word
Count command. The Sector to be programmed must be unlocked (unprotected).
The system then writes the starting address / data combination. This starting address is the first address / data pair to be
programmed, and selects the write-buffer-Line address. The Sector address must match the Write to Buffer Sector Address or the
operation will abort and return to the initiating state. All subsequent address / data pairs must be in sequential order. All write buffer
addresses must be within the same Line. If the system attempts to load data outside this range, the operation will abort and return to
the initiating state.
The counter decrements for each data load operation. Note that while counting down the data writes, every write is considered to be
data being loaded into the write buffer. No commands are possible during the write buffer loading period. The only way to stop
loading the write buffer is to write with an address that is outside the Line of the programming operation. This invalid address will
immediately abort the Write to Buffer command.
Once the specified number of write buffer locations has been loaded, the system must then write the Program Buffer to Flash
command at the Sector Address. The device then goes busy. The Embedded Program algorithm automatically programs and
verifies the data for the correct data pattern. The system is not required to provide any controls or timings during these operations. If
an incorrect number of write buffer locations have been loaded the operation will abort and return to the initiating state. The abort
occurs when anything other than the Program Buffer to Flash is written when that command is expected at the end of the word
count.
The write-buffer embedded programming operation can be suspended using the Program Suspend command. When the Embedded
Program algorithm is complete, the EAC then returns to the EAC standby or Erase Suspend standby state where the programming
operation was started.
The system can determine the status of the program operation by using Data Polling Status, reading the Status Register, or
monitoring the RY/BY# output. See
for information on these status bits. See
for information on these status bits. See
for a diagram of the programming operation.
The Write Buffer Programming Sequence will be Aborted under the following conditions:
Load a Word Count value greater than the buffer size (255).
Write an address that is outside the Line provided in the Write to Buffer command.
The Program Buffer to Flash command is not issued after the Write Word Count number of data words is loaded.
When any of the conditions that cause an abort of write buffer command occur the abort will happen immediately after the offending
condition, and will indicate a Program Fail in the Status Register at bit location 4 (PSB = 1) due to Write Buffer Abort bit location 3
(WBASB = 1). The next successful program operation will clear the failure status or a Clear Status Register may be issued to clear
the PSB status bit.
The Write Buffer Programming Sequence can be stopped by the following: Hardware Reset or Power cycle. However, these using
either of these methods may leave the area being programmed in an intermediate state with invalid or unstable data values. In this
case the same area will need to be reprogrammed with the same data or erased to ensure data values are properly programmed or
erased.
