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C51: USE OF F0 AND F1 IN PSW
Information in this article applies to:
- C51 All Versions
- CX51 All Versions
- C251 All Versions
QUESTION
I am developing an ASIC which contains an 8051 soft core. I want to use one of the user flags in the PSW register, for example F0 (PSW.5) or UD/F1 (PSW.1) to control my hardware.
The flags in PSW are saved on the stack when the register bank is changed or an interrupt service routine is called. Using a bit in another register implies that these other registers need to be saved on the stack.
Therefore my question: Are these flags used by one of the Keil products C51, ISD51, or RTX51?
ANSWER
The F0 flag is used by several arithmetic library routines. The UD/F1 flag is not used by any of the Keil development tools and may be used by your software/hardware.
SEE ALSO
- C51: ?C? LOAD AND STORE LIBRARY ROUTINES
- C51: ?C? LONG/FLOAT MATH LIBRARY ROUTINES
- C51: REGISTER USAGE OVER XBANKING.A51 FUNCTIONS
- GENERAL: SYSTEM ARCHITECTURE AND ASSEMBLY PROGRAMMING
FORUM THREADS
The following Discussion Forum threads may provide information related to this topic.
Last Reviewed: Friday, November 12, 2004
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