MC68HC11E0CFNE3 Datasheet, PDF (200/242 Pages) Freescale Semiconductor, Inc – M68HC11E Family

Main Bootloader Program
[1] START FROM RESET
IN BOOT MODE
INITIALIZATION:
[2]
SP = TOP OF RAM ($01FF)
X = START OF REGS ($1000)
SPCR = $20 (SET DWOM BIT)
BAUD = $A2 (÷ 4; ÷ 4) (7812.5 BAUD @ 2 MHz)
SCCR2 = $C0 (Tx & Rx ON)
TOC1 = DELAY CONSTANT (539 = 4 SCI CHARACTER TIMES)
SEND BREAK [3]
NO _{RECEIVED FIRST CHAR YET ?}
YES
FIRST CHAR = $00 ? ^YES
NO _NOTZERO
YES _{FIRST CHAR = $FF ?}
NO
[5]
[4]
JUMP TO START
OF EEPROM ($B600)
NOTE THAT A BREAK
CHARACTER IS ALSO
RECEIVED AS $00
SWITCH TO SLOWER SCI RATE...
BAUD = $33 (÷13; ÷ 8) (1200 BAUD @ 2 MHz)
CHANGE DELAY CONSTANT...
TOC1 = 3504 (4 SCI CHARACTER TIMES)
BAUDOK
POINT TO START OF RAM ( Y = $0000 ) [6]
[7] WAIT
INITIALIZE TIMEOUT COUNT
[8]
WTLOOP
RECEIVE DATA READY ? ^{YES [9]}
NO
DECREMENT TIMEOUT COUNT
LOOP =
19
CYCLES
NO
TIMED OUT YET ?
[10] YES
STORE RECEIVED DATA TO RAM ( ,Y ) [11]
TRANSMIT (ECHO) FOR VERIFY [12]
POINT AT NEXT RAM LOCATION [13]
PAST END OF RAM ?
NO ^[14]
YES _[15]
STAR
SET UP FOR PROGRAM UTILITY:
X = PROGRAMMING TIME CONSTANT
[16]
Y = START OF EPROM
JUMP TO START
OF RAM ($0000)
[17]
Figure 3. MC68HC711E9 Bootloader Flowchart
M68HC11 Bootstrap Mode, Rev. 1.1
200
Freescale Semiconductor