JS28F256P30B95A datasheet(30/97 Pages) MICRON

30 / 97 page

P30

Datasheet

August 2008

306666-12

Before issuing a new command, the Status Register contents should be examined and

then cleared using the Clear Status Register command. Any valid command can follow,

when word programming has completed.

8.2

Factory Word Programming

Factory word programming is similar to word programming in that it uses the same

commands and programming algorithms. However, factory word programming

enhances the programming performance with VPP = VPPH. This can enable faster

programming times during OEM manufacturing processes. Factory word programming

is not intended for extended use. See Section 13.2, “Operating Conditions” on page 52

for limitations when VPP = VPPH.

Note:

When VPP = VPPL, the device draws programming current from the VCC supply. If VPP is driven

by a logic signal, VPPL must remain above VPPL MIN to program the device. When VPP = VPPH,

the device draws programming current from the VPP supply. Figure 11, “Example VPP Supply

Connections” on page 34 shows examples of device power supply configurations.

8.3

Buffered Programming

The device features a 32-word buffer to enable optimum programming performance.

For Buffered Programming, data is first written to an on-chip write buffer. Then the

buffer data is programmed into the flash memory array in buffer-size increments. This

can improve system programming performance significantly over non-buffered

programming.

When the Buffered Programming Setup command is issued (see Section 6.0,

“Command Set” on page 24), Status Register information is updated and reflects the

availability of the buffer. SR[7] indicates buffer availability: if set, the buffer is

available; if cleared, the buffer is not available. To retry, issue the Buffered

Programming Setup command again, and re-check SR[7]. When SR[7] is set, the

buffer is ready for loading. (see Figure 36, “Buffer Program Flowchart” on page 82).

On the next write, a word count is written to the device at the buffer address. This tells

the device how many data words will be written to the buffer, up to the maximum size

of the buffer.

On the next write, a device start address is given along with the first data to be written

to the flash memory array. Subsequent writes provide additional device addresses and

data. All data addresses must lie within the start address plus the word count.

Optimum programming performance and lower power usage are obtained by aligning

the starting address at the beginning of a 32-word boundary (A[4:0] = 0x00). Crossing

a 32-word boundary during programming will double the total programming time.

After the last data is written to the buffer, the Buffered Programming Confirm command

must be issued to the original block address. The WSM begins to program buffer

contents to the flash memory array. If a command other than the Buffered

Programming Confirm command is written to the device, a command sequence error

occurs and Status Register bits SR[7,5,4] are set. If an error occurs while writing to the

array, the device stops programming, and Status Register bits SR[7,4] are set,

indicating a programming failure.

When Buffered Programming has completed, additional buffer writes can be initiated by

issuing another Buffered Programming Setup command and repeating the buffered

program sequence. Buffered programming may be performed with VPP = VPPL or VPPH

(see Section 13.2, “Operating Conditions” on page 52 for limitations when operating

the device with VPP = VPPH).

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