## Two alternate programs for Example 2.17 of Huang

; Program to sum all odd numbers in a table
; Solution to Example 2.17 of Huang
; Bill Rison
; 1/30/97
.title SUM ODD NUMBERS
EVBRAM = 0x0000 ;0x0000 is start of user ram on 68HC11EVBU
DATA = EVBRAM
PROG = EVBRAM+0x100 ;start program above BUFFALO
N = 20 ;number of entries in table
SUMADDR = 0x20 ;location to put result
.area CODE (ABS)
.org PROG ;set program counter to 0x0100
start: ldx #table ;Reg X points to entry to process
ldab #N ;Initialize loop counter to number of table
stab loop_ctr ; entries
clra ;Hold sum in A-B -- clear to start
clrb
l1: brclr 0,x,#0x01,l2 ;If entry is even (LSB=0), don't sum
addb 0,x ;Entry was odd -- add to ACC B
adca #0 ;Add carry to ACC A to complete 16-bit result
l2: inx ;REG X points to next entry in table1
dec loop_ctr ;Decrement number left to process
bne l1 ;If not done, process next table entry
std sum ;Save result
swi ;Done -- Exit
.area DATA (ABS)
.org DATA
table: .db 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19
.org SUMADDR
sum: .ds 2 ;Save sum here
loop_ctr: .ds 1 ;eight-bit counter of number left to process

; Program to sum all odd numbers in a table
; Solution to Example 2.17 of Huang
; Bill Rison
; 1/30/97
.title SUM ODD NUMBERS
EVBRAM = 0x0000 ;0x0000 is start of user ram on 68HC11EVBU
DATA = EVBRAM
PROG = EVBRAM+0x100 ;start program above BUFFALO
N = 20 ;number of entries in table
SUMADDR = 0x20 ;location to put result
.area CODE (ABS)
.org PROG ;set program counter to 0x0100
start: ldx #table ;Reg X points to entry to process
ldab #N ;ACC B holds number of entries left to process
ldy #0 ;Hold sum in Y -- clear to start
l1: brclr 0,x,#0x01,l2 ;If entry is even (LSB=0), don't sum
ldab 0,x ;Entry was odd -- need to get into B to add to Y
aby ;Add to total
l2: inx ;REG X points to next entry in table1
cpx #(table+N) ;Has pointer gone past end of table?
blo l1 ;If not done, process next table entry
sty sum ;Save result
swi ;Done -- Exit
.area DATA (ABS)
.org DATA
table: .db 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19
.org SUMADDR
sum: .ds 2