Page 321 - Programming Microcontrollers in C

306 Chapter 6 Large Microcontrollers

Here the entries are fairly well explained by the comments. Note
that two additional input files are required by this link file. The vec­
tor table vector.o is a compiled version of the vector listing given
in Listing 6-1. The crts.o object module is an assembled version
of the start-up routine for this machine. Both of these routines must
be written and compiled or assembled for the specific program. Oth­
erwise, the link command file is as discussed in Chapter 5. A version
of crts.s is shown below:
;C STARTUP FOR 68HC16
;Copyright (c) 1991 by COSMIC (France)
;
.external _main, __memory
.external ._main, .__bss__
.public _exit, __stext
.psect _bss
sbss:
.psect _text
__stext:
ldk #.__bss__
tbek
tbxk
tbzk
ldab #0fh ; start of the i/o memory space
tbyk ; put it in y
ldx #sbss ; start of bss
clrd ; to be zeroed
bra mtest ; start loop
bcl:
std 0,x ; clear memory
aix #2 ; next word
mtest:
cpx #__memory ; end of memory ?
blo bcl ; no, continue
aix #1000h ; 4K stack
txs ; for instance
jsr _main,#._main ; call application
_exit:
bra _exit ; loop here if return