Routines
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61838: Cycle a character buffer group forwards and scroll the screen right 8 columns
Used by the routines at 30822 and 60539. Cycles one of the character buffer groups in pages 215-221 forwards depending on the current leftmost column of the play area that is on screen (X=(32766)):
X Character buffer group
8, 64, 120, 176 215
16, 72, 128, 184 216
24, 80, 136, 192 217
32, 88, 144, 200 218
40, 96, 152, 208 219
48, 104, 160, 216 220
56, 112, 168, 224 221
61838 LD A,(32766) 32766 holds X, the x-coordinate of the leftmost column of the play area on screen
61841 SUB 8 A=0, 8, 16, 24, 32, 40 or 48 (depending on the value of X)
61843 SUB 56
61845 JR NC,61843
61847 ADD A,56
61849 RRCA A=215-221
61850 RRCA
61851 RRCA
61852 ADD A,215
61854 LD H,A Point HL at the last byte of the last buffer in the group
61855 LD L,124
61857 LD DE,32632 Copy the last buffer in the group (buffer 5) to 32608 temporarily
61860 LD BC,25
61863 LDDR
61865 LD E,124 Point DE at the last byte of the last buffer in the group
61867 LD D,H
61868 LD C,100 Move buffers 1-4 up into slots 2-5 (thus overwriting buffer 5)
61870 LDDR
61872 LD HL,32632 Copy buffer 5 from its temporary storage location into slot 1
61875 LD C,25
61877 LDDR
61879 JP 59461 Scroll the screen right 8 columns (the routine at 30822 replaces this instruction with a RET)
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