8 Mbit Firmware Hub
SST49LF008A
Data Sheet
Write Lock
PARALLEL PROGRAMMING MODE
The Write-Lock bit, bit 0, controls the lock state described in
Table 7. The default Write status of all blocks after power-
up is write locked. When bit 0 of the Block Locking register
is set, Program and Erase operations for the corresponding
block are prevented. Clearing the Write-Lock bit will unpro-
tect the block. The Write-Lock bit must be cleared prior to
starting a Program or Erase operation since it is sampled at
the beginning of the operation.
Device Operation
Commands are used to initiate the memory operation func-
tions of the device. The data portion of the software com-
mand sequence is latched on the rising edge of WE#.
During the software command sequence the row address
is latched on the falling edge of R/C# and the column
address is latched on the rising edge of R/C#.
The Write-Lock bit functions in conjunction with the hard-
ware Write Lock pin TBL# for the top Boot Block. When
TBL# is low, it overrides the software locking scheme. The
top Boot Block Locking register does not indicate the state
of the TBL# pin.
Reset
A VIL on RST# pin initiates a device reset.
Read
The Write-Lock bit functions in conjunction with the hard-
ware WP# pin for blocks 0 to 6. When WP# is low, it over-
rides the software locking scheme. The Block Locking
register does not indicate the state of the WP# pin.
The Read operation of the SST49LF008A device is con-
trolled by OE#. OE# is the output control and is used to
gate data from the output pins. Refer to the Read cycle
timing diagram, Figure 13, for further details.
Lock Down
Byte-Program Operation
The Lock-Down bit, bit 1, controls the Block Locking regis-
ter as described in Table 7. When in the FWH interface
mode, the default Lock Down status of all blocks upon
power-up is not locked down. Once the Lock-Down bit is
set, any future attempted changes to that Block Locking
register will be ignored. The Lock-Down bit is only cleared
upon a device reset with RST# or INIT# or power down.
Current Lock Down status of a particular block can be
determined by reading the corresponding Lock-Down bit.
Once a block’s Lock-Down bit is set, the Write-Lock bits for
that block can no longer be modified, and the block is
locked down in its current state of write accessibility.
The SST49LF008A device is programmed on a byte-by-
byte basis. Before programming, one must ensure that the
sector, in which the byte which is being programmed exists,
is fully erased. The Byte-Program operation is initiated by
executing a four-byte command load sequence for Soft-
ware Data Protection with address (BA) and data in the last
byte sequence. During the Byte-Program operation, the
row address (A10-A0) is latched on the falling edge of R/C#
and the column Address (A21-A11) is latched on the rising
edge of R/C#. The data bus is latched in the rising edge of
WE#. The Program operation, once initiated, will be com-
pleted, within 20 µs. See Figure 14 for Program operation
timing diagram, Figure 17 for timing waveforms, and Figure
25 for its flowchart. During the Program operation, the only
valid reads are Data# Polling and Toggle Bit. During the
internal Program operation, the host is free to perform addi-
tional tasks. Any commands written during the internal Pro-
gram operation will be ignored.
JEDEC ID Registers
The JEDEC ID registers for the boot device appear at
FFBC0000H and FFBC0001H in the 4 GByte system
memory map, and will appear elsewhere if the device is not
the boot device. Register is not available for read when the
device is in Erase/Program operation. Unused register
location will read as 00H. Refer to the relevant application
note for details. See Table 2 for the device ID code.
©2006 Silicon Storage Technology, Inc.
S71161-11-000
3/06
17
SST [ SILICON STORAGE TECHNOLOGY, INC ]
