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

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[[Category:Spectrum]]
[[Category:Spectrum]]
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{{Template:Spectrum edge connector|A15|A13|D7|[[#ROM disable pins|{{overline|OE}}]]|[[#Key_Slot|SLOT]]|D0|D1|D2|D6|D5|D3|D4|{{overline|INT}}|{{overline|NMI}}|{{overline|HALT}}|{{overline|MREQ}}|{{overline|IORQ}}|{{overline|RD}}|{{overline|WR}}|[[#Power|NC]]|{{overline|WAIT}}|[[#Power|+12{{small|V}}]]|[[#Power|−12{{small|V}}]]|{{overline|M1}}|{{overline|RFS}}|A8|A10|[[#RESET|RESET]]|A14|A12|[[#Power|+5{{small|V}}]]|[[#Power|NC]]|[[#Key_Slot|SLOT]]|0{{small|V}}|0{{small|V}}|[[#CPU_Clock|CKEXT]]|A0|A1|A2|A3|NC|0{{small|V}}|[[#ROM disable pins|{{overline|OE}}]]|{{overline|[[#Disc Controller Signals|DRD]]}}|{{overline|[[#Disc Controller Signals|DWR]]}}|{{overline|[[#Disc Controller Signals|MTR]]}}|{{overline|BUSRQ}}|{{overline|RESET}}|A7|A6|A5|A4|[[#ROM disable pins|NC]]|{{overline|BUSACK}}|A9|A11}}
{{Template:Spectrum edge connector|A15|A13|D7|[[#ROM disable pins|{{overline|OE}}]]|[[#Key Slot|SLOT]]|D0|D1|D2|D6|D5|D3|D4|{{overline|INT}}|{{overline|NMI}}|{{overline|HALT}}|{{overline|MREQ}}|{{overline|IORQ}}|{{overline|RD}}|{{overline|WR}}|[[#Power|NC]]|{{overline|WAIT}}|[[#Power|+12{{small|V}}]]|[[#Power|−12{{small|V}}]]|{{overline|M1}}|{{overline|RFS}}|A8|A10|[[#RESET|RESET]]|A14|A12|[[#Power|+5{{small|V}}]]|[[#Power|NC]]|[[#Key Slot|SLOT]]|0{{small|V}}|0{{small|V}}|[[#CPU Clock|CKEXT]]|A0|A1|A2|A3|NC|0{{small|V}}|[[#ROM disable pins|{{overline|OE}}]]|{{overline|[[#Disc Controller Signals|DRD]]}}|{{overline|[[#Disc Controller Signals|DWR]]}}|{{overline|[[#Disc Controller Signals|MTR]]}}|{{overline|BUSRQ}}|{{overline|RESET}}|A7|A6|A5|A4|[[#ROM disable pins|NC]]|{{overline|BUSACK}}|A9|A11}}
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====Disc Controller Signals====
====Disc Controller Signals====
Unlike the +3, the +2A and +2B have no floppy disc controller. Amstrad's original intention was to produce an external floppy controller addon which would have connected to the expansion port on these computers. Since the [[The Amstrad ASIC|ASIC]] is the same on all three machines, all the decoding logic is already present to generate the disk read/write and motor control signals. These three signals are therefore connected through to the expansion port.
Unlike the +3, the +2A and +2B have no floppy disc controller. Amstrad's original intention was to produce an external floppy controller addon which would have connected to the expansion port on these computers. Since the [[The Amstrad ASIC|ASIC]] is the same on all three machines, all the decoding logic is already present to generate the disk read/write and motor control signals. These three signals are therefore connected through to the expansion port.
These signals occupy the pins which were originally used for the component video signals on the [[ZX_Spectrum_16k/48k_Edge_Connector|16k/48k]] expansion port.
These signals occupy the pins which were originally used for the component video signals on the [[ZX Spectrum 16k/48k Edge Connector|16k/48k]] expansion port.


====RESET====
====RESET====
The RESET signal is an inverted version of the {{overline|RESET}} signal, and is produced by one of the inverters in IC15. The purpose of this signal is unclear since any peripheral could derive it by inverting the {{overline|RESET}} line itself. In the +3 it is connected via a 10k resistor (R76) to the floppy drive select line. This however seems to be an error in the circuit design though it has no adverse effects.
The RESET signal is an inverted version of the {{overline|RESET}} signal, and is produced by one of the inverters in IC15. The purpose of this signal is unclear since any peripheral could derive it by inverting the {{overline|RESET}} line itself. In the +3 it is connected via a 10k resistor (R76) to the floppy drive select line. This however seems to be an error in the circuit design though it has no adverse effects.