| Routines

7632: Insert a pixel column into the number graphic buffer

Used by the routine at 7646. Slides the current contents of the number graphic buffer (at D90B) one pixel to the left, and places the new pixel column into the slot freed up on the right.
Input
A | Pixel column byte
7632 | LD HL,$D91F | Point HL at the end of the buffer at D90B
7635 | RRCA | Discard the baseline bit
7636 | LD C,$07 | We will consider the remaining 7 bits
7638 | LD B,$03 | The buffer is 3 character squares wide
763A | RRCA | Drop a bit into the carry flag
763B | RL (HL) | Pick it up in the buffer and shift the other pixels in this row one to the left
763D | DEC HL
763E | DJNZ $763B
7640 | DEC C | Next bit
7641 | JR NZ,$7638 | Jump back until all 7 bits in the column are done
7643 | RET |