EN29GL064ATB Datasheet, PDF (29/58 Pages) Eon Silicon Solution Inc. – 64 Megabit (8192K x 8-bit / 4096K x 16-bit) Flash Memory Page mode Flash Memory, CMOS 3.0 Volt-only

EN29GL064AT/B
Dynamic Protection Bits
Dynamic Protection Bits are volatile and unique for each sector and can be individually modified. DYBs
only control the protection scheme for unprotected sectors that have their PPBs cleared (erased to “1”).
By issuing the DYB Set or Clear command sequences, the DYBs are set (programmed to “0”) or
cleared (erased to “1”), thus placing each sector in the protected or unprotected state respectively. This
feature allows software to easily protect sectors against inadvertent changes yet does not prevent the
easy removal of protection when changes are needed.
Notes
1. The DYBs can be set (programmed to “0”) or cleared (erased to “1”) as often as needed. When the
parts are first shipped, the PPBs are cleared (erased to “1”) and upon power up or reset, the
DYBs can be set or cleared depending upon the ordering option chosen.
2. If the option to clear the DYBs after power up is chosen, (erased to “1”), then the sectorsmay be
modified depending upon the PPB state of that sector (see Table 7).
3. The sectors would be in the protected state If the option to set the DYBs after power up is chosen
(programmed to “0”).
4. It is possible to have sectors that are persistently locked with sectors that are left in the dynamic
state.
5. The DYB Set or Clear commands for the dynamic sectors signify protected or unprotectedstate of
the sectors respectively. However, if there is a need to change the status of the persistently locked
sectors, a few more steps are required. First, the PPB Lock Bit must be cleared by either putting
the device through a power-cycle, or hardware reset. The PPBs can then be changed to reflect the
desired settings. Setting the PPB Lock Bit once again locks the PPBs, and the device operates
normally again.
6. To achieve the best protection, it is recommended to execute the PPB Lock Bit Set command early
in the boot code and protect the boot code by holding WP#/ACC = VIL. Note that the PPB and DYB
bits have the same function when WP#/ACC = VHH as they do when ACC =VIH.
Persistent Protection Bit Lock Bit
The Persistent Protection Bit Lock Bit is a global volatile bit for all sectors. When set (programmed to
“0”), it locks all PPBs and when cleared (erased to “1”), allows the PPBs to be changed. There is only
one PPB Lock Bit per device.
Notes
1. No software command sequence unlocks this bit, but only a hardware reset or a power-up clears this
bit.
2. The PPB Lock Bit must be set (programmed to “0”) only after all PPBs are configured to the desired
settings.
This Data Sheet may be revised by subsequent versions
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or modifications due to changes in technical specifications.
©2004 Eon Silicon Solution, Inc.,
Rev. C, Issue Date: 2011/12/01
www.eonssi.com