The BBC and Master Computer Public Domain Library

Load IWA with Integer from Address

Submitted by Steve Fewell

Routine: iin
Name: Load Integer from Address
Starting Address: &B1AA
Entry criteria: &2A and &2B (lo, hi) contain the address of the Least Significant (first) byte of a 32-bit Integer variable.
Exit: IWA contains the 32-bit Integer number pointed to by &2A, &2B.

Description:
Loads the IWA with the 32-bit Integer pointed to by the zero page locations &2A (low byte) and &2B (high byte). The bytes are copied most significant byte first. The 2nd byte (which should go into IWA location &2B) is temporally stored in X, as &2B is also being used as the address pointer, and we don't want to corrupt it before we've read the complete Integer variable!

The routine sets A to #&40 to indicate that an Integer number is being processed before exiting.

Disassembly for the Load IWA with Integer from Address routine