EB632 datasheet(92/112 Pages) FREESCALE

92 / 112 page

Functional Differences Between MSC8101 (Mask 2K42A) and MSC8103 (Mask 2K87M), Rev. 2

Freescale Semiconductor

Bootloader Program

;check if the sticky bit is set ( HF7 in HCR (HCR[3]) )

move.w HCR,d4

and #$00001000,d4,d4

;if both of the flags are set start the loading again

and d4,d6

tsteq d6

jf from_host

;if everything is OK jump to the address in r3

jmp

end_of_loading

;load the destination address into r3

jsr load_from_fifo

move.l d5,r3

eor d5,d7

jsr load_from_fifo

; reads 0

jsr load_from_fifo

; reads checksum to d5

;get the checksum into d7.l

;d2 = (0xffff0000 & d7)>>16

extractu #16,#16,d7,d2

;d2 = d2 & 0x0000ffff

and #$0000ffff,d2,d2

;d7 = d7 & 0x0000ffff

and #$0000ffff,d7,d7

;d7 = d7 ^ d2

eor d2,d7

;d2 = (~d7 & 0x0000ffff) = ~checksum

not d7,d2

and #$0000ffff,d2,d2

;get ~checksum into d4

extractu #16,#16,d5,d4

;delete the ~checksum from d5

and #$0000ffff,d5,d5

;if ( checksum_loaded |= Checksum_calculated ) goto set sticky bit

cmpeq d5,d2

nop

iff jsr set_sticky_bit

;clean d4.h

and #$0000ffff,d4,d4

;if ( ~checksum_loaded |= ~Checksum_calculated ) goto set sticky bit

cmpeq d4,d7

nop

iff jsr set_sticky_bit

;set HF4 bit in HCR to show that loading is finished

move.w HCR,d6

or #$8000,d6.l

move.w d6,HCR

EB632 Datasheet(PDF) 92 Page - Freescale Semiconductor, Inc

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