AM29F400B AMD [Advanced Micro Devices], AM29F400B Datasheet - Page 16

• Manufacturer Part Number: AM29F400B
• Description: 4 Megabit (512 K x 8-Bit/256 K x 16-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

WRITE OPERATION STATUS
The device provides several bits to determine the sta-
tus of a write operation: DQ2, DQ3, DQ5, DQ6, DQ7,
and RY/BY#. Table 6 and the following subsections de-
scribe 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 sys-
tem 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 com-
mand 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 pro-
g r a m m i n g d u r i n g E r a s e S u s p e n d . W h e n t h e
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 ap-
proximately 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 al-
gorithm 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 in-
formation on DQ7.
After an erase command sequence is written, if all sec-
tors selected for erasing are protected, Data# Polling
on DQ7 is active for approximately 100 µs, then the de-
vice returns to reading array data. If not all selected
sectors are protected, the Embedded Erase algorithm
erases the unprotected sectors, and ignores the se-
lected 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 illustrates this.
Table 6 shows the outputs for Data# Polling on DQ7.
Figure 4 shows the Data# Polling algorithm.
16
P R E L I M I N A R Y
Am29F400B
Notes:
1. VA = Valid address for programming. During a sector
2. DQ7 should be rechecked even if DQ5 = “1” because
No
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.
DQ7 may change simultaneously with DQ5.
Figure 4. Data# Polling Algorithm
Read DQ7–DQ0
Read DQ7–DQ0
DQ7 = Data?
DQ7 = Data?
Addr = VA
Addr = VA
DQ5 = 1?
START
FAIL
No
Yes
No
Yes
Yes
PASS
21505C-8