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USE OF F0 AND F1 IN PSW

Applies to: C51 C Compiler

Answer


Information in this article applies to:


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

Article last edited on: 2004-11-12 16:16:50

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