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Routines |
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This is a cheap pseudo-random number generator. It returns the bottom nibbles from the bytes at $9000..$90FF, in sequence.
Used by the routine at get_target.
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| random_nibble | CB85 | PUSH HL | Preserve HL | |||||||
| CB86 | LD HL,($C41A) | Point at the prng_pointer (initialised on load to $9000) | ||||||||
| CB89 | INC L | Increment its bottom byte, wrapping at $90FF | ||||||||
| CB8A | LD A,(HL) | Fetch a byte from the pointer | ||||||||
| CB8B | AND $0F | Mask off the bottom nibble | ||||||||
| CB8D | LD ($C41A),HL | Save the incremented prng_pointer | ||||||||
| CB90 | POP HL | Restore HL | ||||||||
| CB91 | RET | Return | ||||||||
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