HC908 Application Note #9
Programming & Operating Cautions

This page describes specific actions or conditions that will cause the need for reprogramming of the HC Monitor program.

The HCmon debug monitor program comes preloaded on the daughtercard and resides in upper memory.  (See Memory Map.)  This area is well away from the application code area that holds the various custom programs of interest, such as Exerciser, VFO, Keyer, Commander, Antenna Analyzer, etc.  Since HCmon is integral to the loading and programming of new user programs into flash memory, anything that messes up HCmon will prevent you from continued use of the daughtercard.

If you do not heed the following cautions, you'll likely need to send the daughtercard back for reprogramming.  (Homebrewers outfitted with HC908 programming hardware such as the Mon08 cable/dongle from PE Micro may perform the HCmon re-programming on their own, of course.)

• Do not attempt programming of HCmon via the 'Load' command -- The HCmon debug monitor cannot be programmed into Flash memory by means of its own 'Load' command. HCmon may only be burned into flash memory by means of special hardware programming cable/dongle such as the PE Micro's "Mon08" device or the "ICS08 Developer Board". 
  
• Do not interrupt the daughtercard during the HCmon 'Load' sequence -- If, during active Loading of a new user application, you reset the daughtercard, interrupt system power, disconnect the serial cable, or otherwise interrupt the data flow of the new software, the data being burned into flash memory will likely be corrupted.  This could cause 
  
• Do not define constants, strings, etc within in the HCmon memory space -- Attempting to define strings, constants or otherwise trying to place executable program code within the memory space reserved for HCmon will likely corrupt HCmon and prevent normal operation from there onward.
  
• Do not develop a user application program that extends into HCmon memory space -- The maximum size of a user software application (i.e., the software programs we write starting at $8000) is about 30 kilobytes. That's a big user program space, but if your program grows and extends higher than $E0FF, you will corrupt the bottom area of HCmon program and the daughtercard will require reprogramming of the monitor.
  
• Be sure to include the software hook for 'HCmon_LCD_Display' routine in all application programs -- A "software hook" is utilized to allow HCmon to display an initial message to the LCD (See App Note #10).  If that hook in the user program (at $803C) is not maintained, or if it is overwritten or significantly modified, the start-up sequence for the daughtercard will be blocked and the system will hang.
  
• In HCmon, do not 'Clear' flash memory without immediately performing a 'Load' of another user program -- The normal sequence of operations in loading a new software program to user memory space using HCmon is to 'Clear' the current application space ($8000-$E0FF) and then 'Load' the new program. If the new program is not loaded, the 'software hook' is not placed where HCmon expects to see it in user space ($803C) and the system will not proceed past the barest of initialization the next time the system is power cycled or reset. Always include the software hook in place
  
• Don't forget to configure the terminal program (TeraTerm) with a 5ms pacing delay for each character -- As instructed in the TeraTerm section of the user manual, it's necessary to configure a 5 millisecond 'pacing' delay to occur after each data byte is sent to the daughtercard during the 'Load' operation.  This delay accounts for not having hardware flow control in the serial link and ensures that the flash programming sequence in HCmon has enough time to complete before another data byte is received. If the pacing character is not configured to be at least 5ms, data overrun will be experienced on the daughtercard which will result in improper/incomplete programming of the new user software application.
  
• Be careful to only "Load" an S Record file into the daughtercard -- Only files with an extension of ".s19" may be burned into user application memory space on the daughtercard. The S Record file contains specific address and checksum information to ensure proper programming of flash memory, and if a different file is selected by mistake (e.g., an .asm file), the boot loader may be instructed to program data into illegal areas of memory space.

Although this list of "cautions" may seem daunting, most are common sense and are rarely encountered during normal operation.  After you get a feel for using the daughtercard and its software tools, safe operation becomes second nature.  .