Utilization of Write Buffer when S29GL-T is Configured in x8 (byte) Mode - KBA224466

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Author: AlbertB_56        Version: **

Translation - Japanese: S29GL-Tがx8(バイト)モードで構成されている場合の書き込みバッファの利用 - KBA224466 - Community Translated (JA)

Question:

How is the entire capacity of the Write Buffer utilized on S29GL-T, configured in x8 (byte) mode, when migrating from the S29GL-P or S29GL-S?

Answer:

With Cypress’ Parallel NOR flash memory products, the capacity of the write buffer ranges from 32 bytes for the S29GL064N, to 512 bytes for the S29GL512T. However, for the S29GL-T device, while the size of the write buffer is independent of whether the parallel data lines are configured in x8 (BYTE) mode or in x16 (WORD) mode, the full 512B write buffer can only be written via one write buffer programming command in x16 mode; two write buffer programming commands are required to write 512B to the write buffer when in x8 mode.

The reason for this is that the word count (WC) argument for the “write to buffer” command is one byte – so WC can count to 256 words in x16 mode (that is, the full 512B write buffer capacity), or 256 bytes in x8 mode (that is, only ½ of the 512B write buffer).

Table 1.  Command Definitions x16

Command Sequence

Cycles

Bus Cycles

First

Second

Third

Fourth

Fifth

Sixth

Seventh

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Addr

Data

Read

1

RA

RD

Reset/ASO Exit

1

XXX

F0

Status Register Read

2

555

70

XXX

RD

Status Register Clear

1

555

71

Word Program

4

555

AA

2AA

55

555

A0

PA

PD

Write to Buffer

6

555

AA

2AA

55

SA

25

WC

WBL

PD

WBL

PD

Program Buffer to Flash

1

SA

29

Thus, for x8 mode, two write buffer programming operations of 256B each must be used to program the full 512B write buffer: select the starting address align with write buffer offset 0 for the first buffer program operation, and; select the starting address to align with write buffer offset 256 for the second buffer program operation.

• If you are migrating from an older device with smaller write buffers (S29GL-N has a 32B write buffer; S29GL-P has a 64B write buffer), then your existing programming command syntax will work without change if the migration maintains either x8 or x16 mode.
• However, if you are migrating from the prior generation x16-only S29GL-S (≥ 128 Mb) with a 512B write buffer, then keeping the x16 configuration with S29GL-T also means no change to your existing programming command syntax.
• When migrating from the x8/x16 S29GL064S with 256B write buffer to the S29GL-T, then no change to your existing programming command syntax is required if the migration maintains either x8 or x16 mode.

Note that when reading the Common Flash Interface (CFI), as detailed in Table 2, the maximum number of bytes in multi-byte (in x8 BYTE mode) write is 256-bytes (0-255 bytes).  The maximum number of words in multi-word (in x16 WORD mode) write is 256-words (0-255 words).

For more details, see the S29GL512T datasheet.

Table 2.  CFI Device Geometry Definition

Word Address	Byte Address	Data	Description
(SA) + 0027h	(SA) + 004Eh	001Bh (1 Gb) 001Ah (512 Mb)	Device Size = 2N byte;
(SA) + 0028h	(SA) + 0050h	0002h	Flash Device Interface Description 0 = x8-only, 1 = x16-only, 2 = x8/x16 capable
(SA) + 0029h	(SA) + 0052h	0000h
(SA) + 002Ah	(SA) + 0054h	0009h	Max. number of byte in multi-byte write = 2N (00 = not supported)
(SA) + 002Bh	(SA) + 0056h	0000h
(SA) + 002Ch	(SA) + 0058h	0001h	Number of Erase Block Regions within device 1 = Uniform Device, 2 = Boot Device
(SA) + 002Dh	(SA) + 005Ah	00XXh	Erase Block Region 1 Information (refer to JEDEC JESD68-01 or JEP137 specifications) 00FFh, 0003h, 0000h, 0002h =1 Gb 00FFh, 0001h, 0000h, 0002h = 512 Mb
(SA) + 002Eh	(SA) + 005Ch	000Xh
(SA) + 002Fh	(SA) + 005Eh	0000h
(SA) + 0030h	(SA) + 0060h	000Xh
(SA) + 0031h	(SA) + 0062h	0000h	Erase Block Region 2 Information (refer to CFI publication 100)
(SA) + 0032h	(SA) + 0064h	0000h
(SA) + 0033h	(SA) + 0066h	0000h
(SA) + 0034h	(SA) + 0068h	0000h
(SA) + 0035h	(SA) + 006Ah	0000h	Erase Block Region 3 Information (refer to CFI publication 100)
(SA) + 0036h	(SA) + 006Ch	0000h
(SA) + 0037h	(SA) + 006Eh	0000h
(SA) + 0038h	(SA) + 0070h	0000h
(SA) + 0039h	(SA) + 0072h	0000h	Erase Block Region 4 Information (refer to CFI publication 100)
(SA) + 003Ah	(SA) + 0074h	0000h
(SA) + 003Bh	(SA) + 0076h	0000h
(SA) + 003Ch	(SA) + 0078h	0000h
(SA) + 003Dh	(SA) + 007Ah	FFFFh	Reserved
(SA) + 003Eh	(SA) + 007Ch	FFFFh
(SA) + 003Fh	(SA) + 007Eh	FFFFh