AM29F400B datasheet(20/43 Pages) AMD

20 / 43 page

Am29F400B

21505E5 November 1, 2006

D A TA

SH EE T

WRITE OPERATION STATUS

The device provides several bits to determine the

status of a write operation: DQ2, DQ3, DQ5, DQ6,

DQ7, and RY/BY#. Table 6 and the following subsec-

tions describe the functions of these bits. DQ7, RY/

BY#, and DQ6 each offer a method for determining

whether a program or erase operation is complete or in

progress. These three bits are discussed first.

DQ7: Data# Polling

The Data# Polling bit, DQ7, indicates to the host

system whether an Embedded Algorithm is in progress

or completed, or whether the device is in Erase Sus-

pend. Data# Polling is valid after the rising edge of the

final WE# pulse in the program or erase command

sequence.

During the Embedded Program algorithm, the device

outputs on DQ7 the complement of the datum pro-

grammed to DQ7. This DQ7 status also applies to

programming during Erase Suspend. When the

Embedded Program algorithm is complete, the device

outputs the datum programmed to DQ7. The system

must provide the program address to read valid status

information on DQ7. If a program address falls within a

protected sector, Data# Polling on DQ7 is active for

approximately 2 µs, then the device returns to reading

array data.

During the Embedded Erase algorithm, Data# Polling

produces a “0” on DQ7. When the Embedded Erase

algorithm is complete, or if the device enters the Erase

Suspend mode, Data# Polling produces a “1” on DQ7.

This is analogous to the complement/true datum output

described for the Embedded Program algorithm: the

erase function changes all the bits in a sector to “1”;

prior to this, the device outputs the “complement,” or

“0.” The system must provide an address within any of

the sectors selected for erasure to read valid status

information on DQ7.

After an erase command sequence is written, if all

sectors selected for erasing are protected, Data#

Polling on DQ7 is active for approximately 100 µs, then

the device returns to reading array data. If not all

selected sectors are protected, the Embedded Erase

algorithm erases the unprotected sectors, and ignores

the selected sectors that are protected.

When the system detects DQ7 has changed from the

complement to true data, it can read valid data at

DQ7–DQ0 on the following read cycles. This is

because DQ7 may change asynchronously with

DQ0–DQ6 while Output Enable (OE#) is asserted low.

Figure 15, Data# Polling Timings (During Embedded

Algorithms), in the “AC Characteristics” section illus-

trates this.

Table 6 shows the outputs for Data# Polling on DQ7.

Figure 4 shows the Data# Polling algorithm.

DQ7 = Data?

Yes

DQ5 = 1?

Yes

FAIL

PASS

Read DQ7–DQ0

Addr = VA

Read DQ7–DQ0

Addr = VA

DQ7 = Data?

START

Notes:

1. VA = Valid address for programming. During a sector

erase operation, a valid address is an address within any

sector selected for erasure. During chip erase, a valid

address is any non-protected sector address.

2. DQ7 should be rechecked even if DQ5 = “1” because

DQ7 may change simultaneously with DQ5.

Figure 4.

Data# Polling Algorithm

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