Reading and Writing program memory

[bigseacow]

I am using PIC87J50, v4.099 so there is no eeprom available. I am attempting to read and write to program memory using read_program_eeprom() and write_program_memory() to set an upgrade flag that can be written by system code and read and written by the bootloader code.

I have in place a boot version which is written in bootloader mode (in bootloader ROM space) and read in system code; this works fine. When I attempt to read the boot version in the boot code I only receive 0xFFFF when using using read_program_eeprom() .

Am I not able to read from the program memory while running in bootloader mode because this is also where the code is executing? Any hints to why this is not working is greatly appreciated.

This code example works from the system code but iTemp16 is only set to FFFF when I use this code in the boot code:

[Douglas Kennedy]

Well, lets pause a second....there is no eeprom and your code uses write program memory but reads with read-eeprom_memory. Is this what you want? The address of eeprom is a high address specific to the PIC device.
For program memory it's size that varies. EEprom has a longer life cycle of writes. Look at the boot loader examples supplied by CCS. They work so start there and move forward with any changes you need. To pass info to and from the bootloader and the application program set aside an area in program memory of just a few bytes for flags.#org will keep the compiler from placing code this area Map the flag variables to this area with these kinds of restrictions
#org DOWN_LOAD_FLAG_ADDR,DOWN_LOAD_FLAG_ADDR+1

#define DEBUG_SPACE 0x400
#define DOWN_LOAD_FLAG_ADDR GETENV("PROGRAM_MEMORY")-DEBUG_SPACE-2
#define WPS_STRUCT_ADDR GETENV("PROGRAM_MEMORY")-DEBUG_SPACE-0x100

#define LOADER_END 0x4FF
#define LOADER_SIZE 0x3FF
#define LOADER_ADDR LOADER_END-LOADER_SIZE

below is a memory map
Note a) I have left space for the CCS IDE debugger
b) the WPS area is written to by the application
since upon reset the application (WPS) needs its calibration data
The PIC is married to calibration data after first compile and download via a device programmer. The application accepts and records calibration data fed into it. Since the calibration data will rarely change program memory storage is chosen. The calibration data is not known at compile time since it depends on the actual external components the PIC will control. The bootloader brings in updated code but leaves the calibration untouched.

[bigseacow]

Thanks for your reply

I believe that combination is what I want, but maybe not since it isn't working. The 87J50 has no EEPROM Data memory, but has built in 128KB program EEPROM memory.

Just to be clear, the boot code is fully working using a physical switch on the PC board to control if boot code or system code enters on startup. I usually put a flag on the onboard data eeprom to indicate to enter bootloader to jump to the system code. Having no data eeprom I am attempting to use program eeprom space to hold the flag. I can successfully write the boot version to program eeprom space in the bootloader and read it back in the system code. When I attempt to read the bootloader version back while still running in the bootloader I get only FFFF, rather than the data that was programmed.