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1C96: THE 'SET PERMANENT COLOURS' SUBROUTINE
The address of this routine is derived from an offset found in the command class table.
This subroutine allows for the current temporary colours to be made permanent. As command class +07 it is in effect the command routine for the six colour item commands.
Input
Output
CLASS_07 1C96 BIT 7,(IY+$01) The syntax/run flag (bit 7 of FLAGS) is read.
1C9A RES 0,(IY+$02) Signal 'main screen' (reset bit 0 of TV-FLAG).
1C9E CALL NZ,TEMPS Only during a 'run' call TEMPS to ensure the temporary colours are the main screen colours.
1CA1 POP AF Drop the return address SCAN_LOOP.
1CA2 LD A,($5C74) Fetch the low byte of T-ADDR and subtract +13 to give the range +D9 to +DE which are the token codes for INK to OVER.
1CA5 SUB $13
1CA7 CALL CO_TEMP_4 Change the temporary colours as directed by the BASIC statement.
1CAA CALL CHECK_END Move on to the next statement if checking syntax.
1CAD LD HL,($5C8F) Now the temporary colour values (ATTR-T and MASK-T) are made permanent (ATTR-P and MASK-P).
1CB0 LD ($5C8D),HL
1CB3 LD HL,$5C91 This is P-FLAG, and that too has to be considered.
1CB6 LD A,(HL)
The following instructions cleverly copy the even bits of the supplied byte to the odd bits, in effect making the permanent bits the same as the temporary ones.
1CB7 RLCA Move the mask leftwards.
1CB8 XOR (HL) Impress onto the mask only the even bits of the other byte.
1CB9 AND %10101010
1CBB XOR (HL)
1CBC LD (HL),A Restore the result.
1CBD RET
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