gnupic: Possible 'gpsim' 16F877 EEPROM Data Write Bug
Subject:
Re: Possible 'gpsim' 16F877 EEPROM Data Write Bug
From:
Snail Instruments ####@####.####
Date:
16 Oct 2002 08:05:59 -0000
Message-Id: <3.0.6.16.20021016074100.0d2f6a82@pop.iol.cz>
> The significant operational disadvantage of leaving the busy loop at the
>end of the subroutine is that during realtime operation the writing of a
>single byte to data memory will stop the program flow for 4-8 mS while
>waiting for the WR flag to clear. If the busy test is left at the entry of
>the subroutine this delay only occurs during multiple writes to data memory
>within 8 mS of each other.
Tom's conclusion is correct, just a side note - if the EEPROM is busy writing data (WR bit set), you don't have read access neither to the EEPROM nor the program memory (of course it doesn't affect program execution, only reading data from program memory). Once I got bitten by this when I stored some strings in program memory and occasionaly got strange characters on the display.
Josef
