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14368 and six seem to be the proper numbers, per my comprehension of Patrick Rak.

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Thomas Harte 2021-04-04 19:52:19 -04:00
parent 5a66956221
commit 1da51bee6c
1 changed files with 4 additions and 9 deletions
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13
Machines/Sinclair/ZXSpectrum/Video.hpp
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@ -88,19 +88,14 @@ template <VideoTiming timing> class Video {
.cycles_per_line = 228 * 2, .cycles_per_line = 228 * 2,
.lines_per_frame = 311, .lines_per_frame = 311,
// i.e. video fetching begins five cycles after the start of the // i.e. video fetching begins six cycles after the start of the
// contended memory pattern below; that should put a clear two // contended memory pattern below; that should put a clear two
// cycles between a Z80 access and the first video fetch. // cycles between a Z80 access and the first video fetch.
.contention_leadin = 5 * 2, .contention_leadin = 6 * 2,
.contention_duration = 129 * 2, .contention_duration = 129 * 2,
// i.e. interrupt is first signalled // i.e. interrupt is first signalled 14368 cycles before the first video fetch.
// 311*228 - 5 - 56543 = 14364 cycles before the beginning of .interrupt_time = (228*311 - 14368) * 2,
// contended accesses.
//
// (which, as above, include a bit of guesswork as to the meaning of
// 'time since interrupt' in the commonly-cited documentation)
.interrupt_time = 56543 * 2,
.delays = { .delays = {
2, 1, 2, 1,