ZX Spectrum edge connector: Difference between revisions

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ZX Spectrum edge connector (view source)

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[[Category:Edge Connectors]]
{{Template:Spectrum edge connector|A15|A13|D7|[[#ROM disable pins|{{overline|OE}}]]|SLOT|D0|D1|D2|D6|D5|D3|D4|{{overline|INT}}|{{overline|NMI}}|{{overline|HALT}}|{{overline|MREQ}}|{{overline|IORQ}}|{{overline|RD}}|{{overline|WR}}|NC|{{overline|WAIT}}|&#43;12v|NC|{{overline|M1}}|{{overline|RFSH}}|A8|A10|NC|A14|A12|&#43;5v|NC|SLOT|0v|0v|[[#CPU_Clock|{{overline|CK}}]]|A0|A1|A2|A3|NC|0v|[[#ROM disable pins|{{overline|OE}}]]|NC|NC|NC|{{overline|BUSRQ}}|{{overline|RESET}}|A7|A6|A5|A4|[[#ROM disable pins|{{overline|ROMCS}}]]|{{overline|BUSACK}}|A9|A11|showzx81pins=true}}
[[Category:Hardware]]
[[Category:Spectrum]]
<!-- end of category list -->
{{Template:Spectrum edge connector|A15|A13|D7|[[#ROM disable pins|{{overline|OE}}]]|SLOT|D0|D1|D2|D6|D5|D3|D4|{{overline|INT}}|{{overline|NMI}}|{{overline|HALT}}|{{overline|MREQ}}|{{overline|IORQ}}|{{overline|RD}}|{{overline|WR}}|NC|{{overline|WAIT}}|&#43;12v|NC|{{overline|M1}}|{{overline|RFSH}}|A8|A10|NC|A14|A12|&#43;5v|NC|SLOT|0v|0v|{{overline|CK}}|A0|A1|A2|A3|NC|0v|[[#ROM disable pins|{{overline|OE}}]]|NC|NC|NC|{{overline|BUSRQ}}|{{overline|RESET}}|A7|A6|A5|A4|[[#ROM disable pins|{{overline|ROMCS}}]]|{{overline|BUSACK}}|A9|A11}}


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==ZX80/81 Compatibility==
==ZX80/81 Compatibility==
The ZX Spectrum expansion connector is related to (and partially compatible with) the earlier [[ZX80/81_Edge_Connector|ZX80 and ZX81 expansion connector]], though only the data bus, low address lines, and a subset of the control bus remain in the same locations relative to the index slot.
The ZX Spectrum expansion connector is related to (and partially compatible with) the earlier [[ZX80/81_Edge_Connector|ZX80 and ZX81 expansion connector]], though only the data bus, low address lines, and a subset of the control bus remain in the same locations relative to the index slot.  Lines not physically present on the ZX80/ZX81 edge connector are shown with underlining of their numbers in the diagram shown here.


==ZX Spectrum model differences==
==ZX Spectrum model differences==
The three main "generations" of the ZX Spectrum each provide a slightly different set of signals on the connector and are described fully in the following articles: [[ZX_Spectrum_16k/48k_Edge_Connector|16/48k]], [[ZX_Spectrum+_128K_Edge_Connector|128k]], [[ZX Spectrum +3/2A/2B Edge Connector|+3/+2A/+2B]].
The three main "generations" of the ZX Spectrum each provide a slightly different set of signals on the connector and are described fully in the following articles: [[ZX Spectrum 16K/48K edge connector|16K/48K]], [[ZX Spectrum+ 128K edge connector|128K/+2]], [[ZX Spectrum +2A/2B, +3/3B edge connector|+2A/+3, +2B, and +3B]].


This article and the table on the right attempts to describe a compatible pinout which is consistent across all models. Only signals and supplies which are present on 'all' models are listed. The remaining pins are designated NC for simplicity but be aware that on different models those pins will in fact be connected.
This article and the table on the right attempts to describe a compatible pinout which is consistent across all models. Only signals and supplies which are present on ''all'' models are listed (with the exception of the notes below). The remaining pins are shown as NC in this table for simplicity but be aware that those pins will carry signals dependent on the model.


An interface which uses only the signals shown should work on any model of ZX Spectrum.
An interface which uses only the signals shown should work on any model of ZX Spectrum.


===ROM disable pins===
====ROM disable pins====
The Spectrum 16/48k and Spectrum+ 128k both provide {{overline|ROMCS}} on lower pin 25. By holding this pin high an external peripheral can prevent the Spectrum's ROM from driving the data bus, and place its own ROM or RAM within the first 16k of the 64k memory space.
The Spectrum 16K/48K and Spectrum+ 128K both provide {{overline|ROMCS}} on lower pin 25. By holding this pin high an external peripheral can prevent the Spectrum's ROM from driving the data bus, and place its own ROM or RAM within the first 16K of the 64K memory space.
 
The +3 and its derivatives however have two physical ROM chips and each have their output enable routed to the expansion port. These two {{overline|OE}} (Output Enable) pins are upper pin 4, and lower pin 15. Upper pin 4 was not connected on any of the earlier models, but lower pin 15 was used for composite video out on the [[ZX Spectrum 16K/48K edge connector#Video Outputs|16K/48K]]. Lower pin 25 ({{overline|ROMCS}}) is not connected on the +3/+2A/+2B and lower pin 15 is unused on the Spectrum 128 or +2.
 
This means that when designing an interface which will page external memory in place of the Spectrum ROM a configuration jumper or similar is required to connect the ROM disable signal to lower pin 15 on a +3, but disconnect it on a 16K/48K.
Applying ROM paging signals to the 16K/48K composite out pin does no permanent damage, but causes burst of patterning on the display.


The +3 and its derivatives however have two physical ROM chips and each have their {{overline|OE}} signal routed to the expansion port. These two {{overline|OE}} pins are upper pin 4, and lower pin 15. Upper pin 4 was not connected on any of the earlier models, but lower pin 15 was used for composite video out on the [[ZX_Spectrum_16k/48k_Edge_Connector#Video_Outputs|16/48k]]. Lower pin 25 ({{overline|ROMCS}}) is not connected on the +3/+2A/+2B and Lower pin 15 is unused on the 128k.
====CPU Clock====
Note that the {{overline|CK}} signal was accidentally left unconnected on the Spanish version of the Spectrum 128.


This means that when designing an interface which will page external memory in place of the Spectrum ROM a configuration jumper or similar is required to connect the ROM disable signal to lower pin 15 on a +3, but disconnect it on a 16/48k.
[[Category:Edge connectors]]
Applying ROM paging signals to the 16/48k composite out pin does no permanent damage, but causes burst of patterning on the display.
[[Category:Hardware]]
[[Category:Spectrum]]
Retrieved from ‘https://sinclair.wiki.zxnet.co.uk/wiki/Special:MobileDiff/1094...1789’

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