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View Full Version : What does the I bit (from the ZCRI field) in an assembly instruction do?



PointDog
10-26-2006, 08:31 AM
Hi all. I am currently looking at migrating some of my designs to the propeller chip, and am trying to get an idea of the architecure of the chip, it all seems pretty straight forward but I am not sure about the I bit in the ZCRI field of the assembly instruction. I have not seen it in any other microcontrollers, but some microprocessors have it as an indirect addressing bit that is set to indicate that the address in the instruction points to a register that holds the address of the destination register, rather than the instruction holding the absolute address of the destination register. What is it for on the propeller?

Thanks in advance.

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Mike Green
10-26-2006, 08:37 AM
The I bit specifies "immediate" rather than indirect. If that bit is set, the source operand is the 9 bit immediate value in the source field of the instruction rather than the contents of the cog long word at that location.

PointDog
10-26-2006, 08:44 AM
Wow, prompt answer! Thanks Mike.