The circuit is nearly indentical to the [[Schneider RS232 Interface]] from 1985, both circuits are using a [[Media:Mostek_3801_Data.pdf|Z80 STI]], both mapped to the same I/O port addresses. Both circuits are driven by the 4MHz signal on the CPC's expansion port, and connect CTS/RTS/DSR/DTR to the same pins, so they are (almost) 100% compatible. Some differences:
* The Schneider circuit additionally implements CHRDET.
* The Schneider circuit contains 2 diodes and 2 diodes capacitors for converting ~8V AC to +8V/-8V DC.
* The Schneider circuit uses only 2 chips for port decoding (the overcomplicated DIY uses 5 chips for exactly the same purpose)
Image:SchneiderSioManualPage2.jpg|Schneider's Schematic (1985)
Image:NoPicture.png|Paul Bauriedl's Schematic (1987)
Image:Tim Riemann RS232.gif|Tim Riemann's Z80 STI Schematic (1996)
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[[File:Rs232cpc.lzh]] - All info and files on topic
[[Category:Peripherals]]