BRIGHT
Microelectronics
Inc.
Preliminary BM29F040
operation is completed the data on DQ7 becomes "1", and the device returns to the read mode. Data
polling must be performed at an address within any of the sectors being erased.
Figure 4 shows the Embedded Erase Algorithm and Figure 11 shows the Sector Erase Waveforms.
Erase Suspend and Resume
The Erase suspend command allows the user to interrupt the sector erase function and then read
data from the other sectors which were not being erased. This command is not applicable during the
Chip erase operation or during the program mode. The Erase suspend command (B0H) will terminate
the Sector erase operation and it may require form 0.1 mS to 70 mS to suspend the erase operation
and go into the read mode (pseudo read mode). The user must use the toggle bit to determine if the
chip has entered the erase suspended read mode, at which time the toggle bit will stop toggling. An
address of a sector not being erased must be used to read the toggle bit. The user must keep the
information whether the device is in pseudo read mode or read mode. Every time an Erase suspend
command followed by an Erase resume command is written the internal counters are reset. The erase
suspend command is allowed during the 100 mS time out window before the actual sector erase
operation starts. The Erase resume command will start the erase operation immediately and there is
no time out window during erase resume. Note that any other command during the time out will reset
the device to read mode.
To resume the Sector erase operation after pseudo read mode the Resume command (30H) should
be written. The sector erase will start immediately. Another Erase suspend command can be written
after the chip has resumed the erase operation. Note that a data "0" can not be programmed back to
"1." Attempting to do so may give erroneous results or may hang up the device. Only an erase
operation can change the data from a "0" to "1".
The system may also write the Autoselect Command during the Erase Suspend mode. This allows the
host system to correctly read the autoselect codes during Erase Suspend since this data is not stored
in the memory array.
Sector Protection
The BM29F040 has a hardware sector protection. This feature will disable both Program and Erase
operation of the protected sector or group of sectors. The device is shipped with all sectors
unprotected.
To verify if a sector is protected, the programming equipment must force VID on the address pin A9,
and A6 = CE = OE = VIL and WE = VIH. Reading the device at a particular sector address (A16,
A17 and A18) and XXX2H will produce 01H at the data outputs for a protected sector. See Figure 14
for the AC Waveforms and Figure 16 for the algorithm.
Please use the appropriate approved Programmer or contact Bright for the BM29F040 Programmers
Guide for the specification for protecting individual sectors.
Sector Unprotection
The BM29F040 also features a sector unprotect mode, so that a protected sector may be
unprotected. All sectors are unprotected at the same time. Please use the appropriate approved
Programmer or contact Bright for the BM29F040 Programmers Guide for the specification to
unprotect the sectors.
It is also possible to determine if a sector is unprotected in the system by writing the autoselect
command and A6 is set to VIH. Performing a read operation at XXX2H and the sector address
(defined by A16, A17 and A18) will produce 00H at the Data outputs for an unprotected sector.
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