If CMOS levels (VCC ± 0.2V) are used to drive the bus and the bus is inactive for 300ns or
more the memory enters Automatic Standby where the internal Supply current is reduced to
the Standby Supply current, ICC2. The Data Inputs/Outputs will still output data if a Bus
Read operation is in progress.
Special bus operations
Additional bus operations can be performed to read the Electronic signature and also to
apply and remove Block Protection. These bus operations are intended for use by
programming equipment and are not usually used in applications. They require VID to be
applied to some pins.
The memory has two codes, the manufacturer code and the device code, that can be read
to identify the memory. These codes can be read by applying the signals listed in Table 2
and Table 3, Bus operations.
Block Protect and Chip Unprotect
Groups of blocks can be protected against accidental Program or Erase. The Protection
groups are shown in Appendix A: Block Addresses, Table 20 and Table 21, Block
Addresses. The whole chip can be unprotected to allow the data inside the blocks to be
The VPP/Write Protect pin can be used to protect the two outermost boot blocks. When
VPP/Write Protect is at VIL the two outermost boot blocks are protected and remain
protected regardless of the Block Protection Status or the Reset/Block Temporary
Unprotect pin status.
Block Protect and Chip Unprotect operations are described in Appendix D: Block Protection.