MC705P6ACPE Datasheet, PDF (59/98 Pages) Freescale Semiconductor, Inc – M68HC05 Microcontrollers

EPROM Bootloader
10.6 EPROM Bootloader
Three port pins are associated with bootloader control functions: PC3, PC4, and PC6. Table 10-2
summarizes their functionality.
Table 10-2. Bootloader Control Pins
PC6
PC4
PC3
1
1
1
1
1
0
1
0
0
Mode
Program/verify
Verify only
Dump MCU EPROM to port A
10.7 Programming from an External Memory Device
In this programming mode, PC5 must be connected to V_SS. PC4 and PC3 are used to select the
programming mode. The programming circuit shown in Figure 10-2 uses an external 12-bit counter to
address the memory device containing the code to be copied. This counter requires a clock and a reset
function. The 12-bit counter can address up to 4 Kbytes of memory, which means that a port pin has to
be used to address the remaining 4 K of the 8-K memory space.
The following procedure explains how to use the programming circuit shown in Figure 10-2 to copy a user
program from an external memory device into the MCU’s EPROM:
1. Program a 2764-type EPROM device with the desired instructions and data. Code programmed
into the 2764 must appear at the same addresses desired in the MC68HC705P6A. Therefore, the
page zero code must start at $0020 and end at $004F, the main body of code must start at $0100
and end at $12FF, and the user vectors must start at $1FF0 and end at $1FFF.
NOTE
The MOR data must appear at $1EFF and $1F00.
2. Install the programmed 2764 device into the programming circuit.
3. Install the MC68HC705P6A to be programmed into the programming circuit.
4. Set the PROGRAM and/or VERIFY switches for the desired operation (an open switch is the active
state) and close the RESET switch to hold the MCU in reset.
5. Make sure that the V_PP source is OFF.
6. Apply the V_DD source to the programming circuit.
7. Apply the V_PP source to the programming circuit.
8. Open the RESET switch to allow the MCU to come out of reset and begin execution of the software
in its internal bootloader ROM.
9. Wait for programming and/or verification to complete (about 40 seconds). The PROGRAM LED will
light during programming and the VERIFY LED will light if verification was requested and was
successful.
10. When complete, close the RESET switch to force the MCU into the reset state.
11. Turn off the V_PP source.
12. Turn off the V_DD source.
13. Remove device(s).
MC68HC705P6A Advance Information Data Sheet, Rev. 2.1
Freescale Semiconductor
59