Elementary assembly lang question...

[Dale Klein]

This is probably an elementary question for those who know assembly.  I 
wouldn't know, I'm still in preschool.

Here is a little section from the T-side of the 8051 LT1.  It has to do 
with the aldl (or maybe the E <-> T side SCI communication?) message 
checksum, I guess...

The question:
	Why / What is the function of line BCD7, branch if carry, _back to the 
same address_?  Is this a hole that the program gets stuck in until some 
interrupt digs it out?  The cop timer gets reset just before (BCB0 to 
BCB6), it wouldn't be waiting for the cop timer to go off, would it?  and 
then the t counter is compared with whatever is in memory 1986 (BCCD to 
BCD1), and then the bcc line I'm wondering about.

	I looked a though the anht hac for an example of a branch back to same 
address, but couldn't find one myself.  Does anyone know of an example of 
this sort of thing?


Thanks,
	Dale

BCB0	CC 55 AA        LBCB0:	ldD	#$55AA
BCB3	B7 10 3A        	staA	l_103a_hc11reg_coprst
BCB6	F7 10 3A        	staB	l_103a_hc11reg_coprst
BCB9	CC 50 A0        	ldD	#$50A0
BCBC	B7 18 06        	staA	L1806
BCBF	F7 18 06        	staB	L1806
BCC2	B6 19 88        	ldaA	L1988
BCC5	81 0F           	cmpA	#$0F
BCC7	22 0E           	bhi	LBCD7
BCC9	26 0E           	bne	LBCD9
BCCB	18 3C           	pushY	
BCCD	18 FE 10 0E     	ldY	l_100ef_hc11reg_tcnt
BCD1	18 BC 19 86     	cmpY	L1986
BCD5	18 38           	popY	
BCD7	24 FE           LBCD7:	bcc	LBCD7
BCD9	F6 10 25        LBCD9:	ldaB	l_1025_hc11reg_tflg2
BCDC	C5 80           	bitB	#%10000000
BCDE	27 09           	beq	@0
BCE0	C6 80           	ldaB	#$80
BCE2	F7 10 25        	staB	l_1025_hc11reg_tflg2
BCE5	4C              	incA	
BCE6	B7 19 88        	staA	L1988
BCE9	B6 10 2E        @0	ldaA	l_102e_hc11reg_scsr
BCEC	85 0E           	bitA	#%00001110
BCEE	27 04           	beq	@1
BCF0	38              	popX	
BCF1	7E BC 18        	jmp	LBC18
;
BCF4	B6 10 2E        @1	ldaA	l_102e_hc11reg_scsr
BCF7	85 20           	bitA	#%00100000
BCF9	27 B5           	beq	LBCB0
BCFB	B6 10 2F        	ldaA	l_102f_hc11reg_scdr
BCFE	16              	tAB	
BCFF	FB 19 8A        	addB	l_198a_cksum
BD02	F7 19 8A        	staB	l_198a_cksum
BD05	39              	ret	


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