AM29F400AT datasheet(14/35 Pages) AMD

14 / 35 page

Am29F400AT/Am29F400AB

PRELIMINARY

accepted and erasure will start. It is recommended that

processor interrupts be disabled during this time to

guarantee this condition. The interrupts can be

re-enabled after the last Sector Erase command

is written. A time-out of 100

µs from the rising edge of

the last WE will initiate the execution of the Sector

Erase command(s). If another falling edge of the WE

occurs within the 100

µs time-out window the timer is

reset. (Monitor DQ3 to determine if the sector erase

timer window is still open, see section DQ3, Sector

Erase Timer.) Any command other than Sector Erase

or Erase Suspend during this period will reset the de-

vice to the read mode, ignoring the previous command

string. In that case, restart the erase on those sectors

and allow them to complete.

(Refer to the Write Operation Status section for DQ3,

Sector Erase Timer operation.) Loading the sector

erase buffer may be done in any sequence and with

any number of sectors (0 to10).

Sector erase does

not require the user to program the

device prior to erase. The device automatically pro-

grams all memory locations in the sector(s) to be

erased prior to electrical erase. When erasing a sector

or sectors the remaining unselected sectors are not af-

fected. The system is

not required to provide any con-

trols or timings during these operations.

The automatic sector erase begins after the 100

µs

time out from the rising edge of the WE pulse for the

last sector erase command pulse and terminates when

the data on DQ7, Data Polling, is “1” (see Write Opera-

tion Status section) at which time the device returns to

the read mode. Data Polling must be performed at an

address within any of the sectors being erased.

Figure 1 illustrates the Embedded Erase Algorithm

using typical command strings and bus operations.

Erase Suspend

The Erase Suspend command allows the user to inter-

rupt a Sector Erase operation and then perform data

reads from a sector not being erased. This command is

applicable ONLY during the Sector Erase operation

which includes the time-out period for sector erase. The

Erase Suspend command will be ignored if written dur-

ing the Chip Erase oper ation or Embedded

Program Algorithm. Writing the Erase Suspend com-

mand during the Sector Erase time-out results in imme-

diate termination of the time-out period and suspension

of the erase operation.

Any other command written during the Erase Suspend

mode

will

ignored

except

the

Er ase

Resume command. Writing the Erase Resume com-

mand resumes the erase operation. The addresses are

“don’t-cares” when writing the Erase Suspend or Erase

Resume command.

When the Erase Suspend command is written during

the Sector Erase operation, the device will take a max-

imum of 15

µs to suspend the erase operation. When

the device has entered the erase-suspended mode,

DQ6 will stop toggling. The user must use the address

of a sector being erased for reading DQ6 to determine

if the erase operation has been suspended. Further

writes of the Erase Suspend command are ignored.

When the erase operation has been suspended, the

device defaults to the erase-suspend-read mode.

Reading data in this mode is the same as reading from

the standard read mode except that the data must be

read

from

sectors

that

hav e

not

been

erase-suspended.

To resume the operation of Sector Erase, the Resume

command (30H) should be written. Any further writes of

the Resume command at this point will be ignored. An-

other Erase Suspend command can be written after the

chip has resumed erasing.

Write Operation Status

Table 8.

Write Operation Status

Notes:

1. D8–D15 = Don’t Care for x16 mode.

2. DQ4 for AMD internal use only.

Status

DQ7

DQ6

DQ5

DQ3

In Progress

Auto-Programming

DQ7

Toggle

Program/Erase in Auto-Erase

Toggle

Exceeded

Time Limits

Auto-Programming

DQ7

Toggle

Program/Erase in Auto-Erase

Toggle

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