Motorola MC68VZ328 用户手册
Bootstrap Mode Operation
Bootstrap Mode
17-5
17.1.6
Application Programming Example
The code shown in Example 17-2 can be used to calculate a CRC value. The example demonstrates how
assembly code is assembled and downloaded to system RAM.
assembly code is assembled and downloaded to system RAM.
Example 17-2. Application Programming Example
section code
START:
copy clr.l d1
copy clr.l d1
;d1 is used to count the number of words copied.
clr.w d2 ;d2 is used to count the number of words copied.
nextwd move.w (a0,d2),d6
move.w d6,(a1)+
add.l #2,d1 ;Count the number of words copied.
add.w #2,d2 ;Count the number of words copied.
cmpi.w #16,d2
blt nextwd ;until the whole section has been copied.
clr.w d2
cmp.l d0,d1 ;Copy the next word (nextwd)
blt nextwd ;until the whole section has been copied.
add.l #2,d1 ;Count the number of words copied.
add.w #2,d2 ;Count the number of words copied.
cmpi.w #16,d2
blt nextwd ;until the whole section has been copied.
clr.w d2
cmp.l d0,d1 ;Copy the next word (nextwd)
blt nextwd ;until the whole section has been copied.
crc clr.l D0
lp2 add.l (A0)+,D0
lp2 add.l (A0)+,D0
cmp.l A0,A1
bpl.b lp2
nop
rts
bpl.b lp2
nop
rts
After assembling and linking the program in Example 17-2, generate the following s-record file.
S0030000FC
S1134000428142423C30200032C6548154420C4228
S113401000106DF04242B2806DEA4280D098B3C87D
S10940206AFA4E714E75B0
S9030000FC
S1134000428142423C30200032C6548154420C4228
S113401000106DF04242B2806DEA4280D098B3C87D
S10940206AFA4E714E75B0
S9030000FC
Run the DOS program STOB.EXE to convert the preceding s-records to bootstrap format.
0000400010428142423C30200032C6548154420C42
000040101000106DF04242B2806DEA4280D098B3C8
00004020066AFA4E714E75
000040101000106DF04242B2806DEA4280D098B3C8
00004020066AFA4E714E75
Download the preceding b-record file to the target system using the UART port in bootstrap mode. Since
this b-record file will be loaded into system RAM, initialize the system by downloading an init b-record
file.
this b-record file will be loaded into system RAM, initialize the system by downloading an init b-record
file.
To run the preceding program after it is downloaded to RAM, issue an execution b-record “0000400000”,
where 00004000 is the start address of the program and the last two zeros identify the record as an
execution b-record and not a data record.
where 00004000 is the start address of the program and the last two zeros identify the record as an
execution b-record and not a data record.
To resume bootstrap mode operation after running a program, make the last instruction in the application
program a
program a
jmp $FFFFFF5A
to start receiving a new b-record.
Any b-record may be entered in a RS-232 terminal environment, but when a key is pressed, the character
produced by the keystroke is sent to the bootloader to be assembled. Although the backspace capability is
not implemented, the b-record can be terminated at any time by pressing the ENTER key. As long as a
program execution b-record is not issued, the MC68VZ328 will remain in bootstrap mode.
produced by the keystroke is sent to the bootloader to be assembled. Although the backspace capability is
not implemented, the b-record can be terminated at any time by pressing the ENTER key. As long as a
program execution b-record is not issued, the MC68VZ328 will remain in bootstrap mode.