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how to enable xdata in P87C51RD+
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Farhan Arshad Posted
29-Oct-2004 06:51 GMT Toolset
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 how to enable xdata in P87C51RD+Farhan Arshad
hito use on chip xram of my p87c51RD+. I have made following changes in my code which are recomended here. http://www.keil.com/support/docs/1758.htm but my code stuck on this loop. IDATALOOP: MOV @R0,A DJNZ R0,IDATALOOPregards Farhan I have also posted this messege on http://www.8052.com/forum/read.phtml?id=79977&top=79977 |
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Jon Ward Posted
29-Oct-2004 07:03 GMT Toolset
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RE: how to enable xdata in P87C51RD+ Jon Ward
That is the loop in the startup code that clears memory. Are you sure the program is STUCK in this loop?IDATALOOP: MOV @R0,A DJNZ R0,IDATALOOP The DJNZ instruction is a decrement and jump it non-zero. So, if the program is actually STUCK in this look, it means that R0 never decrements down to 0. Jon |
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Graham Cole Posted
29-Oct-2004 14:32 GMT Toolset
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RE: how to enable xdata in P87C51RD+ Graham Cole
This bit of code may fail if the selected register bank is not zero. If, for example, register bank 1 is selected then when R0 is equall to 8 the instruction:
MOV @R0,A
Will clear R0. The following DJNZ instruction will set R0 to 0xFF and the code will loop forever.
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Keil Support, Intl. Posted
2-Nov-2004 12:51 GMT Toolset
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RE: how to enable xdata in P87C51RD+ Keil Support, Intl.
But this code runs after Reset. Reset ensures that the register bank 0 is selected.
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Oleg Sergeev Posted
2-Nov-2004 13:16 GMT Toolset
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RE: how to enable xdata in P87C51RD+ Oleg Sergeev
hi,Maybe you should use MOVX instead MOV and DPTR instead R0. http://www.8052.com/forum/read.phtml?id=80001 Regards, Oleg |
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mark hickman Posted
3-Nov-2004 01:24 GMT Toolset
C51 |
RE: how to enable xdata in P87C51RD+ mark hickman
Hi Farhan,I am a little unclear as to what your problem(s) is/are. If you know that you are getting stuck on the loop to clear IDATA, I am suprised as this is tried and tested code and you will not get stuck in an infinite loop even if you start with R0 set to 00h, then why not just set :- IDATALEN EQU 00H so this code is not included so you can see if your code gets past this point? If you ar using the PHILIPS P87c51rd+ then I hope you have not copied verbatim what is shown in "1758.htm" as this quite clearly relates to a diffent chip, so for you chip you should have :- XDATASTART EQU 00000H XDATALEN EQU 0300H to clear the onchip EXTRAM which according to the data sheet is enabled by default. Also you should not include (if you have added it) this line :- ANL 0B1h, #01h show in the keil app note. Alternativly if you want to disable the internal EXTRAM then you should include the following line:- ORL 08Eh, #02h which will set the EXTRAM bit within the AUXR register. |
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