Serial transfer problem

Dec 22, 2006 5 Replies
E

I am using a DS89C440 flash micro running at 29.491Mhz with 64k of external RAM and no external ROM. I am running my serial port using timer-1 for baud rate generator at



19200baud. My source computer is a P4-3Ghz running winxp-pro and my program for sending data to the micro is Visual C++ 6.0 For some reason I dont under stand, not all the data I send to the micro gets there. My serial receive code for the micro is below: ; ; ***** Get job data from PC ***** ; getpc: mov dptr,#1000h ;set dptr to data area getpc1: jnb ri,getpc1 mov a,sbuf ;get char from port clr ri movx @dptr,a ;save data to memory inc dptr mov a,dph cjne a,#20h,getpc1 ;receive 8319 bytes mov a,dpl cjne a,#7fh,getpc1 ljmp loop ;top of program

Any ideas???


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M

How many bytes are you losing? a random amount? do you expect to receive

207f bytes?
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E

I am allways expecting to receive 207Fh bytes because that is how many are allways transmitted by the PC program. The number of bytes missing seems random. Sometimes I only miss a few bytes and other times I am missing quite a few.

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H

Hi Ed,

Two thoughts.

1 Are you SURE the PC is sending 3819 bytes each time? Prove with another PC running HyperTerminal. 2 Do you have any interrupts running on your micro?

Jay

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M

Make the code an interrupt service routine......

RXint:

mov a,sbuf ;get char from port movx @dptr,a ;save data to memory inc dptr mov a,dph cjne a,#20h,getpc1 ;receive 8319 bytes mov a,dpl cjne a,#7fh,getpc1

set complete flag here disable rx interrupts

get1pc rti

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E

I am sure of the number of bytes transferred and tested with 2nd pc using hyperterm. I am using no interrupts on the micro, my serial uses polling only. I dont see how making the serial routing interrupt driven would help. I think it would increase the possibility of missing bytes more possible due to the extra instructions. I am doing nothing else while receiving data from the pc.

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