Serial S-Record Bootloader - Motorola M68EVB912B32 User Manual

The EEPROM bootloader occupies 1 Kbyte of erase-protected Flash EEPROM starting at
address $FC00. It is invoked when the EVB is started in BOOTLOAD mode (W3-1 and W4-1).
The bootloader may be used to program user code into byte-erasable (byte-erasable) EEPROM
starting at address $0D00 and/or Flash EEPROM starting at address $8000. The user program in
Flash EEPROM may then serve as the "boot" (startup) code when the board is placed in EVB
mode (W3-0 and W4-0) or POD mode (W3-0 and W4-1) and reset.
D-Bug12 is overwritten when using Flash EEPROM for user code. But since the bootloader
itself cannot be overwritten, it is always available for loading new user code or reloading
D-Bug12.
An additional 1 Kbyte of Flash EEPROM, starting at address
$F800, is reserved for future expansion of the bootloader. Thus,
user code may only occupy the 30 Kbytes from $8000 to $F7FF.
Programs loaded and used in this manner cannot be used for true
emulation of an application. Refer to the restrictions in section 3.9.
Use of the EEPROM bootloader is described in the following sections.

SERIAL S-RECORD BOOTLOADER

The bootloader contains a serial S-Record loader that can load assembled code from the host
computer into either Flash EEPROM or byte-erasable EEPROM.
communications with the host computer via the EVB's RS-232C interface. The only special
requirements for the host computer's communications program are:
• It must operate at 9600 baud.
• It must wait for the prompt string '*' (the ASCII asterisk character) before sending a
line of text to the EVB. This "handshaking" is necessary because of the variable
amount of time required to program each S-Record into byte-erasable or Flash
EEPROM.
typically requires less than 180 µs per byte but can take as long as 3.5 ms.
When the EVB is restarted with jumpers W3 and W4 set for BOOTLOAD mode, the EEPROM
68EVB912B32UM/D
APPENDIX E
EEPROM BOOTLOADER
NOTES
Byte-erasable EEPROM requires 10 ms per byte.
EEPROM BOOTLOADER
It uses the SCI for
Flash EEPROM
E-1