DS87C530_1 Datasheet, PDF (28/44 Pages) Dallas Semiconductor – EPROM/ROM Micro with Real Time Clock

EPROM LOCK BITS Table 11
DS87C530/DS83C530
LEVEL
LOCK BITS
PROTECTION
LB1 LB2 LB3
1
U
U
U No program lock. Encrypted verify if encryption table was
programmed.
2
P
U
U Prevent MOVC instructions in external memory from reading
program bytes in internal memory. EA is sampled and latched
on reset. Allow no further programming of EPROM.
3
P
P
U Level 2 plus no verify operation. Also, prevent MOVX
instructions in external memory from reading SRAM (MOVX)
in internal memory.
4
P
P
P Level 3 plus no external execution.
EPROM PROGRAMMING CONFIGURATION Figure 5
ROM-SPECIFIC FEATURES
The DS83C530 supports a subset of the EPROM features found on the DS87C530.
SECURITY OPTIONS
Lock Bits
The DS83C530 employs a lock that restricts viewing of the ROM contents. When set, the lock will
prevent MOVC instructions in external memory from reading program bytes in internal memory. When
locked, the EA pin is sampled and latched on reset. The lock setting is enabled or disabled when the
devices are manufactured according to customer specifications. The lock bit cannot be read in software,
and its status can only be determined by observing the operation of the device.
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