Routines
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61882: Cycle a character buffer group backwards and scroll the screen left 8 columns
Used by the routines at 30822 and 60539. Cycles one of the character buffer groups in pages 215-221 backwards depending on the current leftmost column of the play area that is on screen (X=(32766)):
X Character buffer group
0, 56, 112, 168 215
8, 64, 120, 176 216
16, 72, 128, 184 217
24, 80, 136, 192 218
32, 88, 144, 200 219
40, 96, 152, 208 220
48, 104, 160, 216 221
61882 LD A,(32766) 32766 holds X, the x-coordinate of the leftmost column of the play area on screen
61885 SUB 56 A=0, 8, 16, 24, 32, 40 or 48 (depending on the value of X)
61887 JR NC,61885
61889 ADD A,56
61891 RRCA A=215-221
61892 RRCA
61893 RRCA
61894 ADD A,215
61896 LD H,A Point HL at the first byte of the first buffer in the group
61897 LD L,0
61899 LD DE,32608 Copy the first buffer in the group (buffer 1) to 32608 temporarily
61902 LD BC,25
61905 LDIR
61907 LD E,B Point DE at the first byte of the first buffer in the group
61908 LD D,H
61909 LD C,100 Move buffers 2-5 down into slots 1-4 (thus overwriting buffer 1)
61911 LDIR
61913 LD HL,32608 Copy buffer 1 from its temporary storage location into slot 5
61916 LD C,25
61918 LDIR
61920 JP 59406 Scroll the screen left 8 columns (the routine at 30822 replaces this instruction with a RET)
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