Automatic Start-Up Of Your Application

When you reboot the board, the autostart code will run automatically. It will configure the baud rate, set up the interrupt vectors, and then jump to your code. The board will be permanently dedicated to run your application, unless you use the flash erase jumper to restore it to the original, erased condition.

Default Settings: Code at 0x8000, Baud Rate is 115200 Bits/sec

This code resides in the memory from 0xF600 to 0xF7FF (the last 512 bytes of the flash), so your application must not use that memory. Of course, the full source code is available if you need that memory, or the default settings are not correct for your application.

Configuring Your Code's Build Location

--code-loc 0x8000

If you are using AS31, you will need to place a ".org" directive at the beginning of your code. For example:

        .org    0x8000

Before downloading the autostart.hex file, try using PAULMON2's "J" (Jump) command to jump to your code at 0x8000. If that works and you are ready to permanently dedicate the board to automatically running your application, then you are ready to download the autostart.hex file.

Erasing The Flash

Figure 1: Once you've downloaded AUTOSTART.HEX, this FLASH ERASE jumper is the only way to return to PAULMON2's interactive menus.

If you wish to return to PAULMON2's menus, you must use the flash erase jumper to erase the flash rom. Short the upper two pins together and keep them shorted while you press the RESET button. When the board resets, the flash rom will be erased and you will be returned to the PAULMON2 prompt, where you may further develop your application or use the board for a new purpose.

Customizing Baud Rate Setup

.equ    baud_const, 255         ;115200 baud w/ 22.1182 MHz          
;.equ   baud_const, 254         ;57600 baud w/ 22.1182 MHz
;.equ   baud_const, 253         ;38400 baud w/ 22.1182 MHz
;.equ   baud_const, 250         ;19200 baud w/ 22.1182 MHz
;.equ   baud_const, 244         ;9600 baud w/ 22.1182 MHz

If you need a different baud rate, you must compute the value for "baud_const", using this formula:

baud_const = 256 - (115200 / baud_rate)

Customizing Application Startup

; set this to the location where your application code begins.
; With SDCC, this is the value you used for --code-loc
; With AS31, this is the .org locations where your code was built

.equ    application, 0x8000


; set this to where you'd like these two auto-startup routines
; to be placed in the flash.  Normally 0xF600 is a good choice,
; to place this at the end of the flash (where it is least likely    
; to conflict with the space for your application).

.equ    location, 0xF600

Of course, the complete source code is provided, so you can edit the code to perform any customized startup you need. The normal code simply writes seven LJMPs into RAM in the 0x2000, so that the interrupts will jump to your interrupt code in the flash rom, and then jumps to your program's starting location.

For example, if the additional LJMP interrupt latency is not acceptable, you could modify the code to instead copy your interrupt handler to the RAM. Or perhaps you are not using interrupts and you want to avoid writing to the RAM during a reboot, in which case you could simply delete that section.

Download The Autostart Code

• autostart.hex - Ready to use HEX file with default settings.
• autostart.asm - Source code with comments.
• autostart.zip - ZIP archive with both of these.