Controlling Access To The Otprom During Normal Operation; Controlling Access To The Otprom During Programming Modes - Intel 8XC196NT User Manual

8XC196NT USER'S MANUAL
15.3.1.1

Controlling Access to the OTPROM During Normal Operation

During normal operation, the lock bits in CCB0 control read and write accesses to the OTPROM.
Table 15-2 describes the options. You can program the CCBs using any of the programming
methods.
Table 15-2. Memory Protection for Normal Operating Mode
Read Protect Write Protect
LOC1 (CCR0.7) LOC0 (CCR0.6)
1
1
0
0
Clearing CCB0.6 enables write protection. With write protection enabled, a write attempt causes
the bus controller to cycle through the write sequence, but it does not enable V
the OTPROM. This protects the entire OTPROM array from inadvertent or unauthorized pro-
gramming.
Clearing CCB0.7 enables read protection and also write protects the security key to protect it
from being overwritten. With read protection enabled, the bus controller will not read from pro-
tected areas of OTPROM. An attempt to load the slave program counter with an external address
causes the device to reset itself. Because the slave program counter can be as much as four bytes
ahead of the CPU program counter, the bus controller might prevent code execution from the last
four bytes of internal memory. The interrupt vectors and CCBs are not read protected because
interrupts can occur even when executing from external memory.
15.3.1.2

Controlling Access to the OTPROM During Programming Modes

For programming modes, three levels of protection are available:
•
prohibit all programming
•
prohibit all programming, but permit authorized ROM dumps
•
prohibit serial port programming, but permit authorized ROM dumps, auto programming,
and slave programming
15-4
No protection. Run-time programming is permitted, and the entire
1
OTPROM array can be read.
Write protection only. Run-time programming is disabled, but the
0
entire OTPROM array can be read.
Read protection. Run-time programming is disabled. If program
1 execution is external, only the interrupt vectors and CCBs can be
read. The security key is write protected.
Read and write protection. Run-time programming is disabled. If
0 program execution is external, only the interrupt vectors and CCBs
can be read.
Protection Status
or write data to
PP