ZX Spectrum +2A/2B, +3/3B edge connector: Difference between revisions

ZX Spectrum +2A/2B, +3/3B edge connector (view source)

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 ====ROM disable pins====
-All the previous models of ZX Spectrum have a single ROM chip which could be disabled to facilitate paging in external memory by pulling the !ROMCS line high. The +2A/+3 and +3B however have two ROM chips and brings them out to independent pins on the expansion port. The old !ROMCS pin (Lower pin 25) is not used, and instead Upper pin 4 and Lower pin 15 are used. These pins were both unused on the [[128k+|ZX Spectrum 128K Edge Connector]], however Lower pin 15 was used for composite video out on the [[16k/48k|ZX Spectrum 16k/48k Edge Connector]].
+All the previous models of ZX Spectrum have a single ROM chip which could be disabled to facilitate paging in external memory by pulling the !ROMCS line high. The +2A/+3 and +3B however have two ROM chips and brings them out to independent pins on the expansion port. The old !ROMCS pin (Lower pin 25) is not used, and instead Upper pin 4 and Lower pin 15 are used. These pins were both unused on the [[ZX Spectrum 128K Edge Connector|128k+]], however Lower pin 15 was used for composite video out on the [[ZX Spectrum 16k/48k Edge Connector|16k/48k]].
 ====Disc Controller Signals====