ZLF645 MAXIM [Maxim Integrated Products], ZLF645 Datasheet - Page 81

• Manufacturer Part Number: ZLF645
• Description: Flash MCUs with Learning Amplification
• Manufacturer: MAXIM [Maxim Integrated Products]

19-4572; Rev 0; 4/09
Flash Code Protection Against External Access
Flash Code Protection Against Accidental Program and Erasure
The Flash Controller limits Flash Access capabilities of the ICP and Flash Byte Program-
ming Interfaces based upon the Flash read/write protect bits in User Option Byte 1. By
programming these bits, you can configure the Flash Controller to block page 3 informa-
tion area erasures, main memory reads, and main memory page erasures and programming
as initiated through the ICP or Byte Programming Interfaces of the ZLF645. For more
information, see
As mentioned previously, the ZLF645 products provide several levels of protection
against accidental program and erasure of the Flash main memory contents by ICP and
CPU accesses through the Flash Controller. Through the Flash Controller’s register
locking mechanism, page select redundancy, and sector level protection control, the
ZLF645 products provide protection against accidental program and erasure of the Flash
main memory contents by CPU and ICP accesses, except that for the ICP sector level
protection is ignored. Similar levels of protection are in place for the Flash Information
Area, minus the sector level protection.
Sector Based Flash Protection
For CPU initiated Flash main memory accesses, programming/erase protection is possible
on a sector level basis through programming of the Flash Controller’s Sector Protect
(FSEC) register. For all ZLF645 products, each sector contains 16 pages (of 512 bytes
each).
The Sector Protect (FSEC) register controls the protection state of each Flash sector. This
register is address-shared with the Page Select register. It can only be accessed with the
Flash Controller in ‘locked’ state. With the Flash Controller in ‘locked’ state, writing the
Flash Control (FCTL) register with a value
Protect register to be written. The next write performed to Bank F, Register Address
then targets the Flash Controller’s Sector Protect (FSEC) register.
The Sector Protect register is initialized to 0 on reset, putting each sector into an
unprotected state. When a bit in the Sector Protect register is written to 1, the
corresponding sector within the Flash memory can no longer be programmed or erased if
for operations initiated by the CPU. Operations through the ICP are unaffected by the
Part Number
ZLF645xxxxx32
ZLF645xxxxx64
Table 85
Number of Sectors
on page 174.
8
4
5EH
enables the Flash Controllers Sector
ZLF645 Series Flash MCUs
Product Specification
Flash Controller Overview
02H
73