S71GS256 datasheet(68/195 Pages) SPANSION

68 / 195 page

S29GLxxxN MirrorBitTM Flash Family

S29GLxxxN_MCP_A1 December 15, 2004

Advan ce

In form ati o n

local Spansion representative. Word programming is supported for backward

compatibility with existing Flash driver software and for occasional writing of in-

dividual words. Use of Write Buffer Programming is strongly recommended for

general programming use when more than a few words are to be programmed.

The effective word programming time using Write Buffer Programming is much

shorter than the single word programming time. Any word cannot be pro-

grammed from “0” back to a “1.” Attempting to do so may cause the device

to set DQ5 = 1, or cause the DQ7 and DQ6 status bits to indicate the operation

was successful. However, a succeeding read will show that the data is still “0.”

Only erase operations can convert a “0” to a “1.”

Unlock Bypass Command Sequence

The unlock bypass feature allows the system to program words to the device

faster than using the standard program command sequence. The unlock bypass

command sequence is initiated by first writing two unlock cycles. This is followed

by a third write cycle containing the unlock bypass command, 20h. The device

then enters the unlock bypass mode. A two-cycle unlock bypass program com-

mand sequence is all that is required to program in this mode. The first cycle in

this sequence contains the unlock bypass program command, A0h; the second

cycle contains the program address and data. Additional data is programmed in

the same manner. This mode dispenses with the initial two unlock cycles required

in the standard program command sequence, resulting in faster total program-

ming time. Table 12 shows the requirements for the command sequence.

During the unlock bypass mode, only the Unlock Bypass Program and Unlock By-

pass Reset commands are valid. To exit the unlock bypass mode, the system

must issue the two-cycle unlock bypass reset command sequence. (See Table

12).

Write Buffer Programming

Write Buffer Programming allows the system write to a maximum of 16 words/32

bytes in one programming operation. This results in faster effective programming

time than the standard programming algorithms. The Write Buffer Programming

command sequence is initiated by first writing two unlock cycles. This is followed

by a third write cycle containing the Write Buffer Load command written at the

Sector Address in which programming will occur. The fourth cycle writes the sec-

tor address and the number of word locations, minus one, to be programmed. For

example, if the system will program 6 unique address locations, then 05h should

be written to the device. This tells the device how many write buffer addresses

will be loaded with data and therefore when to expect the Program Buffer to Flash

command. The number of locations to program cannot exceed the size of the

write buffer or the operation will abort.

The fifth cycle writes the first address location and data to be programmed. The

write-buffer-page is selected by address bits AMAX–A4. All subsequent address/

data pairs must fall within the selected-write-buffer-page. The system then

writes the remaining address/data pairs into the write buffer. Write buffer loca-

tions may be loaded in any order.

The write-buffer-page address must be the same for all address/data pairs loaded

into the write buffer. (This means Write Buffer Programming cannot be performed

across multiple write-buffer pages. This also means that Write Buffer Program-

ming cannot be performed across multiple sectors. If the system attempts to load

programming data outside of the selected write-buffer page, the operation will

abort.)

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