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Universe: NwS1

[BBC Master version]

Name: NwS1 [Show more] Type: Subroutine Category: Universe Summary: Flip the sign and double an INWK byte
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * NWSPS calls NwS1

Flip the sign of the INWK byte at offset X, and increment X by 2. This is used by the space station creation routine at NWSPS.
Arguments: X The offset of the INWK byte to be flipped
Returns: X X is incremented by 2
.NwS1 LDA INWK,X \ Load the X-th byte of INWK into A and flip bit 7, EOR #%10000000 \ storing the result back in the X-th byte of INWK STA INWK,X INX \ Add 2 to X INX RTS \ Return from the subroutine