MC68HC08AZ60 Datasheet, PDF (151/452 Pages) Motorola, Inc – Advance Information

Freescale Semiconductor, Inc.
Monitor ROM (MON)
Functional Description
Security
A security feature discourages unauthorized reading of ROM locations
while in monitor mode. The host can bypass the security feature at
monitor mode entry by sending eight security bytes that match the bytes
at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain
user-defined data.
NOTE: Do not leave locations $FFF6–$FFFD blank. For security reasons, enter
data at locations $FFF6–$FFFD even if they are not used for vectors.
During monitor mode entry, the MCU waits after the power-on reset for
the host to send the eight security bytes on pin PA0.
V_DD
4096 + 32 CGMXCLK CYCLES
RST
24 CGMXCLK CYCLES
PA7
256 CGMXCLK CYCLES (ONE BIT TIME)
FROM HOST
PA0
1
4
1
1
2
4
1
FROM MCU
NOTE: 1 = Echo delay (2 bit times)
2 = Data return delay (2 bit times)
4 = Wait 1 bit time before sending next byte.
Figure 6. Monitor Mode Entry Timing
If the received bytes match those at locations $FFF6–$FFFD, the host
bypasses the security feature and can read all ROM locations and
execute code from ROM. Security remains bypassed until a power-on
reset occurs. After the host bypasses security, any reset other than a
power-on reset requires the host to send another eight bytes. If the reset
was not a power-on reset, the security remains bypassed regardless of
the data that the host sends.
11-mon
MOTOROLA
MC68HC08AZ60 — Rev 1.0
Monitor ROM (MON)
151
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