16

Am29F800T/Am29F800B

8/18/97

PR E L IM IN A R Y

Write Operation Status

Table 8.

Hardware Sequence Flags

Notes:

1. DQ2 can be toggled when sector address applied is that of an erasing sector. Conversely, DQ2 cannot be toggled when the

sector address applied is that of a non-erasing sector. DQ2 is therefore used to determine which sectors are erasing and

which are not.

2. These status flags apply when outputs are read from the address of a non-erase-suspended sector.

3. If DQ5 is high (exceeded timing limits), successive reads from a problem sector will cause DQ2 to toggle.

DQ7: Data Polling

The Am29F800 device features Data Polling as a

method to indicate to the host that the embedded algo-

rithms are in progress or completed. During the Em-

bedded Program Algorithm, an attempt to read the

device will produce the complement of the data last

written to DQ7. Upon completion of the Embedded Pro-

gram Algorithm, an attempt to read the device will pro-

duce the true data last written to DQ7. During the

Embedded Erase Algorithm, an attempt to read the de-

vic e will produc e a “0” at t h e DQ 7 out put .

Upon completion of the Embedded Erase Algorithm an

attempt to read the device will produce a “1” at the DQ7

output. The flowchart for Data Polling (DQ7) is shown

in Figure 3.

For chip erase, the Data Polling is valid after the rising

edge of the sixth WE pulse in the six write pulse se-

quence. For sector erase, the Data Polling is valid after

the last rising edge of the sector erase WE pulse. Data

Polling must be performed at sector addresses within

any of the sectors being erased and not a protected

sector. Otherwise, the status may not be valid.

Just prior to the completion of Embedded Algorithm op-

erations DQ7 may change asynchronously while the

output enable (OE) is asserted low. This means that the

device is driving status information on DQ7 at

one instant of time and then that byte’s valid data at the

ne x t in s t a n t o f ti m e . D e pe nd i n g on w h e n th e

system samples the DQ7 output, it may read the status

or valid data. Even if the device has completed

the Embedded Algorithm operations and DQ7 has a

valid data, the data outputs on DQ0–DQ6 may be still

invalid. The valid data on DQ0–DQ7 will be read on the

successive read attempts.

The Data Polling feature is only active during the Em-

bedded Programming Algorithm, Embedded Erase Al-

gorithm, or sector erase time-out (see Table 7).

See Figure 11 for the Data Polling timing specifications

and diagrams.

DQ6: Toggle Bit

The Am29F800 also features the “Toggle Bit” as a

method to indicate to the host system that the embed-

ded algorithms are in progress or completed.

During an Embedded Program or Erase Algorithm cy-

cle, successive attempts to read (OE toggling) data

from the device at any address will result in DQ6 tog-

gling between one and zero. Once the Embedded Pro-

gram or Erase Algorithm cycle is completed, DQ6 will

stop toggling and valid data will be read on

the next

successive attempt. During programming, the Toggle

Bit is valid after the rising edge of the fourth WE pulse

in the four write pulse sequence. For chip erase, the

Toggle Bit is valid after the rising edge of the sixth WE

pulse in the six write pulse sequence. For Sector erase,

the Toggle Bit is valid after the last rising edge of the

sector erase WE pulse. The Toggle Bit is active during

the sector erase time-out.

Either CE or OE toggling will cause DQ6 to toggle. In

addition, an Erase Suspend/Resume command will

Status

DQ7

DQ6

DQ5

DQ3

DQ2

RDY/BSY

In Progress

Byte Programming

DQ7

Toggle

0

0

No Tog

0

Program/Erase in Auto-Erase

0

Toggle

0

1

(Note 1)

0

Erase

suspend

mode

Erase sector address

1

No Tog

0

1

Toggle

1

Non-erase sector

address

Data

Data

Data

Data

Data

1

Program in erase suspend

DQ7

(Note 2)

Toggle

0

1

1

(Note 1)

0

Exceeded

Time

Limits

Byte Programming

DQ7

Toggle

1

0

No Tog

0

Program/Erase in Auto-Erase

0

Toggle

1

1

(Note 3)

0

Program in erase suspend

DQ7

Toggle

1

1

(Note 3)

0