00001 *************************
00002 *
00003 * XPCLS.ASM
00004 * MDJ 09-24-90
00005 *
00006 * CLEARS THE PMODE SCREEN
00007 *
00008 *************************
00009 *
00010 * U AND S STACKS MUST
00011 * ALREADY BE INITIALIZED
00012 *
00013 * XPCLS CLEARS THE SCREEN
00014 * TO THE BACKGROUND COLOR
00015 * AND REQUIRES NO ENTRY
00016 * CONDITIONS
00017 *
00018 * XPCLSS MUST BE ENTERED
00019 * WITH THE COLOR DESIRED
00020 * (0-3) IN REGISTER B
00021 *
00022 *************************
00023 *
00024 * REF. PAGE B54 EXTENDED
00025 * COLOR BASIC UNRAVELLED
00026 *
00027 *************************
00028 *
00029 BAKCOL  EQU     $B3     BACKGROUND COLOR
00030 BEGGRP  EQU     $BA     START OF CURRENT GRAPHICS PAGE
00031 ENDGRP  EQU     $B7     END OF CURRENT GRAPHICS PAGE
00032         ORG     $3BDC
00033 XPCLS   LDB     BAKCOL  LOAD BACKGROUND COLOR
00034 XPCLSS  LDA     #$55    EACH BYTE = FOUR 2-BIT SUBNIBBLES
00035         MUL             MULTIPLY BY COLOR
00036         LDX     BEGGRP  GET STARTING ADDRESS
00037 XPCLSA  STB     ,X+     SET BYTE TO COLOR & BUMP POINTER
00038         CMPX    ENDGRP  AT END OF PAGE?
00039         BNE     XPCLSA  GO IF NO
00040 ZEND    RTS
00041         END
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
