Freescale Semiconductor, Inc.
EPROM/OTPROM (PROM)
No LED is illuminated during this routine. Further, the end of the routine
does not mean that the SEC bit was verified. To ensure that security is
properly enabled, attempt to perform another verify routine. If the green
LED does not light, the PROM has been secured properly.
9.4.6 Load Program into RAM and Execute
In the load program in RAM and execute routine, user programs are
loaded via the SCI port and then executed. Data is loaded sequentially
starting at address $0050. After the last byte is loaded, control is
transferred to the RAM program starting at $0051. The first byte loaded
is the count of the total number of bytes in the program plus the count
byte. The program starts at location $0051 in RAM. During initialization,
the SCI is configured for eight data bits and one stop bit. The baud rate
is 4800 with a 2-MHz crystal or 9600 with a 4-MHz crystal.
To load a program into RAM and execute it, take these steps:
1. Set switch 1 in the ON position (restores VDD).
2. Connect VPP to VDD.
3. Set switches S3, S5, and S6 in the OFF position.
4. Set switch S4 in the ON position.
5. Set switch 2 in the OUT position (routine is activated).
The downloaded program starts executing as soon as the last byte is
received by the SCI.
Execution of the routine can be held off by setting the byte count in the
count byte (the first byte loaded) to a value greater than the number of
bytes to be loaded. After loading the last byte, the firmware waits for
more data. Program execution does not begin. At this point, placing
switch 2 in the RESET position resets the MCU with the RAM data intact.
Any other routine can be entered, including the one to execute the
program in RAM, simply by setting switches S3–S6 as necessary to
select the desired routine, then setting switch 2 in the OUT position.
Technical Data
114
MC68HC705C8A — Rev. 3
EPROM/OTPROM (PROM)
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