|
Routines |
| Prev: 0E9B | Up: Map | Next: 0ECD |
|
The address of this routine is found in the parameter table.
The one hundred and seventy six pixel lines of the display are dealt with one by one.
|
||||
| COPY | 0EAC | DI | The maskable interrupt is disabled during COPY. | |
| 0EAD | LD B,$B0 | The 176 lines. | ||
| 0EAF | LD HL,$4000 | The base address of the display. | ||
|
The following loop is now entered.
|
||||
| COPY_1 | 0EB2 | PUSH HL | Save the base address and the number of the line. | |
| 0EB3 | PUSH BC | |||
| 0EB4 | CALL COPY_LINE | It is called 176 times. | ||
| 0EB7 | POP BC | Fetch the line number and the base address. | ||
| 0EB8 | POP HL | |||
| 0EB9 | INC H | The base address is updated by 256 locations for each line of pixels. | ||
| 0EBA | LD A,H | Jump forward and hence round the loop again directly for the eight pixel lines of a character line. | ||
| 0EBB | AND $07 | |||
| 0EBD | JR NZ,COPY_2 | |||
|
For each new line of characters the base address has to be updated.
|
||||
| 0EBF | LD A,L | Fetch the low byte. | ||
| 0EC0 | ADD A,$20 | Update it by +20 bytes. | ||
| 0EC2 | LD L,A | The carry flag will be reset when 'within thirds' of the display. | ||
| 0EC3 | CCF | Change the carry flag. | ||
| 0EC4 | SBC A,A | The A register will hold +F8 when within a 'third' but +00 when a new 'third' is reached. | ||
| 0EC5 | AND $F8 | |||
| 0EC7 | ADD A,H | The high byte of the address is now updated. | ||
| 0EC8 | LD H,A | |||
| COPY_2 | 0EC9 | DJNZ COPY_1 | Jump back until 176 lines have been printed. | |
| 0ECB | JR COPY_END | Jump forward to the end routine. | ||
| Prev: 0E9B | Up: Map | Next: 0ECD |