by | hgskiing_fully_ldirs_run.skool | Routines |
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28234: READ_KEYBOARD Keyboard detection routine. Also does other things BEFORE looking at the keyboard. Uses documented QZIP keys. Also allows Interface 2 1234 and 6789 keys to be used instead (undocumented). And allows S key to pause, any bottom row key resumes (also undocumented). Also checks H and G keys – if both are pressed, restarts the game by setting 24249 Uses variable at 24248 and DEMO_OR_GAME_MODE variable at 24249 INPUT: no parameters OUTPUT: B = ONE and only ONE of 0 (UP), 1 (RIGHT), 2 (DOWN), 3 (LEFT) on RETurn Game variables changed: 24262 – these probably all relate to the location of Horace 24261 24260 24220 24249 DEMO_OR_GAME_MODE CALLS: 28077 Call DO_SOME_ATTRIBUTE_WORK Game variables read but not changed 24248 only BITs 210 used ?
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| 28234 | LD BC,1271 | B = 4, C = 247 – C used for keyboard check later | ||
| 28237 | LD DE,24248 | Check 24248 | ||
| 28240 | LD A,(DE) | A = (24248) | ||
| 28241 | AND A | Test if any bits are set, result in A | ||
| 28242 | JR Z,28335 | If 24248 is zero, A AND A is 0, then jump to 28335 (CHECK_PAUSE_ACTIVATE) | ||
| 28244 | BIT 0,A | 24248 is not zero, at least one bit was set in 24248, so check BIT 0 | ||
| 28246 | JR NZ,28256 | If BIT 0 of 24248 is 1, jump to 28256 | ||
| 28248 | CP 2 | BIT 0 is zero, so check if BIT 1 is set (only BIT 1) | ||
| 28250 | JR Z,28297 | If 24248 = 2 (10 binary), then jump to 28297 | ||
| 28252 | LD B,0 | If A (24248)!= 2 set B = 0 | ||
| 28254 | JR 28299 | Jump to 28299 | ||
| 28256 | CP 5 | BIT 0 of 24248 is 1 if we are here, is A = 5? | ||
| 28258 | JR Z,28285 | If A (24248) = 5 BIN 00000101 then jump to 28285 | ||
| 28260 | LD HL,24262 | HL = 24262 | ||
| 28263 | LD A,(HL) | A = (HL) | ||
| 28264 | AND A | A AND A | ||
| 28265 | JR NZ,28269 | If A AND A is non-zero (any of the bits set), jump to 28269 | ||
| 28267 | LD (HL),20 | 24262 is 0, so set 24262 = 20 | ||
| 28269 | DEC (HL) | (HL)– | ||
| 28270 | LD A,(24261) | A = (24261) | ||
| 28273 | JR NZ,28279 | If (24261) is non-zero, go to 28279 | ||
| 28275 | XOR 3 | A is 0, so 00 XOR 11 is 11 (3 decimal) | ||
| 28277 | OR 1 | A = 3 (11 binary), so 11 OR 01 is 11 | ||
| 28279 | LD B,A | B = A = 3 (11) | ||
| 28280 | LD (24261),A | Set 24261 = A = 3 or non-zero original value of 24261 from 28270 | ||
| 28283 | JR 28299 | Jump to 28299 | ||
| 28285 | CALL 28077 | A was 5 from 28258, so now DO_SOME_ATTRIBUTE_WORK | ||
| 28288 | AND 3 | Only want bits 10 of A, discard the rest | ||
| 28290 | BIT 0,A | Test only BIT 0 | ||
| 28292 | JR Z,28318 | Jump to READ_KEYBOARD if BIT 0 of A is ZERO | ||
| 28294 | LD B,A | If BIT 0 of A is 1, set B = A | ||
| 28295 | JR 28299 | Jump to 28299 | ||
| 28297 | LD B,2 | 24248 = A = 2, jump here from 28250 | ||
| 28299 | LD HL,24260 | 24248 != 2, B already set to 0 | ||
| 28302 | DEC (HL) | 24260– | ||
| 28303 | JR NZ,28318 | If A != 0, jump to 28318 | ||
| 28305 | LD (HL),90 | |||
| 28307 | LD A,(DE) | A = 24248 (again) | ||
| 28308 | INC A | A = A + 1 | ||
| 28309 | CP 5 | Subtract 5 from A to compare | ||
| 28311 | LD (DE),A | 24248 = A + 1 | ||
| 28312 | JR C,28318 | If A > 5 then jump to 28318 | ||
| 28314 | XOR A | A <= 5, so set A = 0 | ||
| 28315 | LD (24220),A | Set 24220 = 0 | ||
| 28318 | XOR A | READ_KEYBOARD A !=0 if came from 28303, so set A = 0 | ||
| 28319 | IN A,(254) | |||
| 28321 | AND 31 | Use only 5 rightmost bits | ||
| 28323 | CP 31 | If all 5 43210 bits are 1 then no key pressed | ||
| 28325 | RET Z | If no key pressed then return | ||
| 28326 | XOR A | A = 0 | ||
| 28327 | LD (24220),A | Set 24220 to be zero | ||
| 28330 | INC A | A = 1 | ||
| 28331 | LD (24249),A | Set DEMO_OR_GAME_MODE to be 1 (GAME) | ||
| 28334 | RET | And return (GAME must have started?) | ||
| 28335 | LD A,253 | CHECK_PAUSE_ACTIVATE 24248 was zero, so jumped here | ||
| 28337 | IN A,(254) | Read keyboard A – G half-row | ||
| 28339 | AND 2 | Use only S key (BIT 1) | ||
| 28341 | JR NZ,28363 | If S key is pressed, BIT 1 is zero, so AND 2 is non-zero, so go to 28363 | ||
| 28343 | LD A,127 | S_KEY_PRESSED Bottom right half-row B to SPACE | ||
| 28345 | IN A,(254) | |||
| 28347 | AND 31 | Discard bits 765 as meaningless. Use only bits 43210 | ||
| 28349 | CP 31 | If all bits 43210 are 1 = 31, and no key pressed. | ||
| 28351 | JR NZ,28363 | If zero, all bits 1. Otherwise at least one key was pressed, so jump to CHECK_H_KEY | ||
| 28353 | LD A,254 | Bottom left half-row CAPS SHIFT to V | ||
| 28355 | IN A,(254) | |||
| 28357 | AND 31 | Discard bits 765 as meaningless | ||
| 28359 | CP 31 | If all bits 43210 are 1, no key pressed | ||
| 28361 | JR Z,28343 | LOOP_PAUSE If no key pressed, jump back to S_KEY_PRESSED – 28343 – no bottom row key pressed | ||
| 28363 | LD A,191 | CHECK_H_KEY This is H to ENTER half-row | ||
| 28365 | IN A,(254) | |||
| 28367 | AND 16 | Check only bit 4 which is H key | ||
| 28369 | JR NZ,28383 | If H is pressed, bit 4 is ZERO, AND 16 is ZERO – jump to CHECK_MOVEMENT_KEYS | ||
| 28371 | LD A,253 | CHECK_G_KEY H key has been pressed | ||
| 28373 | IN A,(254) | Read keyboard A – G half-row | ||
| 28375 | AND 16 | Check only bit 4 which is G key | ||
| 28377 | JR NZ,28383 | If G is pressed, bit 4 is ZERO, AND 16 is ZERO – jump to CHECK_MOVEMENT_KEYS | ||
| 28379 | INC A | A is zero if 28377 did not jump, so set A = 1 | ||
| 28380 | LD (24249),A | DEMO_OR_GAME_MODE set to GAME Mode = 1 which starts a new game | ||
| 28383 | LD DE,57327 | CHECK_MOVEMENT_KEYS D = 223, E = 239 | ||
| 28386 | LD A,D | CHECK_RIGHT_KEYS Y to P half-row of keyboard | ||
| 28387 | IN A,(254) | |||
| 28389 | BIT 0,A | Check P key | ||
| 28391 | JR Z,28407 | If BIT 0 is ZERO, P was pressed, then jump to 28407 | ||
| 28393 | LD A,E | Top right half-row 6 to 0 | ||
| 28394 | IN A,(254) | |||
| 28396 | BIT 3,A | Check 7 key | ||
| 28398 | JR Z,28407 | If BIT 3 is ZERO, 7 was pressed, then jump to 28407 | ||
| 28400 | LD A,C | C = 247 | ||
| 28401 | IN A,(254) | Read from top right half-row 1 to 5 keys | ||
| 28403 | BIT 1,A | Check 2 key (BIT 1) | ||
| 28405 | JR NZ,28409 | If 2 key was pressed, BIT 1 is ZERO, jump to 28409 | ||
| 28407 | LD B,1 | GO_RIGHT_KEY_PRESSED One of the “Go right” keys was pressed (P,7,2) – set B = 1 | ||
| 28409 | LD A,C | CHECK_LEFT_KEYS C = 247 from first LD BC at 28234 | ||
| 28410 | IN A,(254) | Read from top right half-row 1 to 5 keys | ||
| 28412 | BIT 0,A | BIT 0 is 1 key | ||
| 28414 | JR Z,28430 | If 1 key is pressed, BIT 0 is 0, jump to GO_LEFT_KEY_PRESSED | ||
| 28416 | LD A,D | D = 223 from 28383 which is executed in all cases | ||
| 28417 | IN A,(254) | 223 represents Y to P keys | ||
| 28419 | BIT 2,A | BIT 2 is the I key | ||
| 28421 | JR Z,28430 | Bit 2 will be 0 if I key is pressed, so jump to GO_LEFT_KEY_PRESSED | ||
| 28423 | LD A,E | E = 239 from 28383 | ||
| 28424 | IN A,(254) | 239 represents 6 to 0 keys | ||
| 28426 | BIT 4,A | BIT 4 is the innermost (leftmost) key, which is 6 key | ||
| 28428 | JR NZ,28432 | If it is pressed, it will be zero, so do not jump and enter GO_LEFT_KEY_PRESSED | ||
| 28430 | LD B,3 | GO_LEFT_KEY_PRESSED – set B = 3 | ||
| 28432 | LD A,E | CHECK_UP_KEYS E = 239 from 28383 | ||
| 28433 | IN A,(254) | Checking 6 to 0 half row of keys | ||
| 28435 | BIT 1,A | BIT 1 is 9 key | ||
| 28437 | JR Z,28454 | If 9 key is pressed, BIT 1 will be zero, so jump to UP_KEY_PRESSED | ||
| 28439 | LD A,251 | Checking 1 to 5 half row of keys | ||
| 28441 | IN A,(254) | |||
| 28443 | BIT 0,A | BIT 0 is outermost key which is Q | ||
| 28445 | JR Z,28454 | If Q key is pressed, BIT 0 will be zero, so jump to UP_KEY_PRESSED | ||
| 28447 | LD A,C | C = 247 from first LD BC at 28234 | ||
| 28448 | IN A,(254) | Checking 1 to 5 half row of keys | ||
| 28450 | BIT 3,A | BIT 3 is 4 key | ||
| 28452 | JR NZ,28456 | If it is pressed, it will be zero, so do not jump and execute next line | ||
| 28454 | LD B,0 | UP_KEY_PRESSED | ||
| 28456 | LD A,C | CHECK_DOWN_KEYS C = 247 from first LD BC at 28234 | ||
| 28457 | IN A,(254) | Checking 1 to 5 half row of keys | ||
| 28459 | BIT 2,A | BIT 2 is 3 key | ||
| 28461 | JR Z,28477 | If 3 key is pressed, BIT 2 will be zero, so jump to DOWN_KEY_PRESSED | ||
| 28463 | LD A,254 | CAPS SHIFT to V half-row of keys | ||
| 28465 | IN A,(254) | |||
| 28467 | BIT 1,A | Check BIT 1 which is Z key | ||
| 28469 | JR Z,28477 | If Z is pressed, A will be 0, so jump to DOWN_KEY_PRESSED | ||
| 28471 | LD A,E | E = 239 from 28383 | ||
| 28472 | IN A,(254) | Check 6 to 0 keys | ||
| 28474 | BIT 2,A | BIT 2 is 8 key | ||
| 28476 | RET NZ | If BIT is NOT zero, then return without signalling down key. | ||
| 28477 | LD B,2 | DOWN_KEY_PRESSED | ||
| 28479 | RET | B = ONE and only ONE of 0 (UP), 1 (RIGHT), 2 (DOWN), 3 (LEFT) on RETurn | ||
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END READ_KEYBOARD
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