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/* Original serial interface (1985) */ Nothing bad about an external PSU!
[[Image:Amstrad RS232.jpg|thumb|right|250px|The Pace RS232 interface, as sold by Amstrad]]
The main difference between the interfaces is that they contain different firmware, and the older one required an external power supply. === Original serial interface (1985) === Amstrad's first serial interface was one of the original peripherals released for the CPC. It was remarkable (in a bad way) for the necessity for an external, brick-like power supply.
Software was supplied on ROM, mostly comprising utility commands for hobbyists rather than a comms application per se - though there was limited terminal emulation for connecting to the then-popular [[Prestel]] service]. The original, UK version included commands for file transfer entitled |SUCK and |BLOW, which used a proprietary Amstrad format similar to [[XModem]]-1k but, annoyingly, subtly incompatible. These commands were reputedly renamed for the US edition to avoid causing offence.
The French company [[M.E.R.C.I.]] sold a custom version of this interface, replacing the original 8k ROM with an 16k Rom adding a [http://en.wikipedia.org/wiki/Minitel minitel] emulator.
Because of the external power supply and the poor quality of the software, this model failed to establish itself as the "standard" serial interface in the way that (say) the [[DDI-1]] did for disc drives. This allowed other serial interfaces to flourish, such as those sold by [[Cirkit]] and [[KDS]].
=== Pace serial interface (1986) === As a result, Amstrad dropped their original design and instead chose to remanufacture a [[PACE]] design. This included improved hardware (a more compact interface thanks to SMD components and no external PSU) and vastly superior software. However, this redesign also reduced the quality of RS232 signalling by using 0V/5V output voltage instead of -12V/12V.
The software Amstrad/Pace version was a ROM version of Pace's terminal utility, announced on [[Commstar]]:File:ACU8612006. This was a user-friendly program with standard [[XModemjpg|Amstrad Computer User, Dec 1986, page 6]] file transfer functions. However, one foolish design decision was the idea of using a 24x80 screen with a single-line status display - though presenting a good user interfaceA review occured in Amstrad Computer User, this forced the use of software rather than hardware scrollingApril 1987, making the interface unusable for terminal emulation at any speed above 2400 baudpages 46 and 47.
== I/O Ports ==
Here are the I/O Ports (same for original and Pace version): FADCh Amstrad RS323 RS232 [[Z80-DART/Z80-SIO chip|Z8470 (Z80 DART) ]] Channel A Data (R/W) FADDh Amstrad RS323 RS232 [[Z80-DART/Z80-SIO chip|Z8470 (Z80 DART) ]] Channel A Control/Status (R/W) FADEh Amstrad RS323 RS232 [[Z80-DART/Z80-SIO chip|Z8470 (Z80 DART) ]] Channel B Data (R/W) FADFh Amstrad RS323 RS232 [[Z80-DART/Z80-SIO chip|Z8470 (Z80 DART) ]] Channel B Control/Status (R/W) FBDCh Amstrad RS323 RS232 [[8253 chip|8253]] Baudrate Timer 0 Channel A TX Clock (R/W) FBDDh Amstrad RS323 RS232 [[8253 chip|8253]] Baudrate Timer 1 Channel A RX Clock (R/W) FBDEh Amstrad RS323 RS232 [[8253 chip|8253]] Baudrate Timer 2 Channel B RX/TX Clock (R/W) FBDFh Amstrad RS323 RS232 [[8253 chip|8253 ]] Baudrate Timer 0-2 Control Registers (W)
Note: Some interfaces might use a Z80 SIO (which is backwards compatible to the Z80 DART).
== Alternative software ==
The limitations of the [[Commstar ]] software, and the desire to use more recently developed file transfer protocols (such as [[XModem]]-1k, [[YModem]] and [[ZModem]]) meant that many users chose to use their Amstrad serial interface with third-party software. This included: * [[Ansiterm]] - a fast AMSDOS utility (also known as ANSI.ARC)* [[Charley's Comms ROM]] - sideways ROM capable of 4800 baud terminal emulation* [[ZMP]] - ZModem file transfer under CP/M A vast range of comms software was available for [[CP/M]], including [[Bulletin board|bulletin board]] hosts, offline readers (notably [[CRR]] - CP/M Read and Reply), and many terminals. == 8250 Information (probably nonsense) == '''Below is information about the 8250 UART chip. As far as known, the Amstrad Serial Interface does NOT use that chip, a 8253 yes, but not a 8250. No idea why that information is here...?''' Like the original interface, the Pace design used an 8250 [[UART]] chip (really???), which was reliable up to 9600 baud and could sometimes function at faster speeds. The possibility has been discussed of replacing this with a pin-compatible 16550 and gaining even faster transfer speeds, but this is not believed to have been tested. This [http://www.systemed.net/pcw/cps8256.html webpage about the CPS8256] (the Amstrad serial interface for the PCW) also includes some CPC information. Caution: that webpage seems to be confused/bugged. There is no 8250 chip used at all. Baudrate MSB/LSB are exchanged, and for both CPC and PCW, the clock source should be 2MHz instead of 1.84375MHz, etc. [http://en.wikipedia.org/wiki/8250_UART Link to Article on Wikipedia about the 8250 UART used (or rather NOT used???) in the interface] == Manual == [[Original Amstrad RS232 interface|Manual of the original RS232 by Amstrad (OCR)]]
== Pictures ==
<gallery caption="Amstrad 's older original serial interface">Image:amstrad RS232C.jpg|The original, flawed Amstrad serial interfaceImage:Amstrad rs232 1.jpg|The original, flawed Amstrad serial interfaceImage:Amstrad rs232 2.jpg|The original, flawed Amstrad serial interface
Image:Amstrad rs232 power1.jpg|The original powersupply that came with the interface
File:Amstrad RS232.jpg|Newer Amstrad/Pace Interface
File:NoPictureAmstrad_RS232_Pace_Interface.gifjpg|Circuit Board of new Pace InterfaceFile:Amstrad_RS232_Pace_PCB_Top.jpg|PCB TopFile:Amstrad_RS232_Pace_PCB_Bottom.jpg|PCB BottomFile:ACU8701002.jpg|Advert (ACU, January 1987)
</gallery>
</gallery>
== Manuals == * [[CategoryMedia:HardwareRS232C Serial Interface (Amsoft UK) Manual.pdf|RS232C Serial Interface (Amsoft UK) Manual]] {{EN}} {{PDF}}* [[Media:RS232C Interface Serie (Amsoft FR) Manual.pdf|RS232C Interface Serie (Amsoft FR) Manual]] {{FR}} {{PDF}}* [[Original Amstrad RS232 interface|Manual of the original RS232 by Amstrad (OCR)]]* [[Media:RS232 (Pace) Manual.pdf|RS232 (Pace) Manual]] {{EN}} {{PDF}} == Downloads == * [[Media:RS232101.ZIP|ROM Image for original version]] - 8K ROM* [[Media:RS232Mercitel14.rom|ROM Image for Mercitel version]] - 16K ROM* [[Media:AmstradPaceSerialInterfaceCommstarRomImage.zip|ROM Image for Pace version]] - Commstar 32K ROM (two 16K banks)* [[Media:PACE232.ZIP|ROM Image for Pace version]] - Commstar 32K ROM [[Category:Peripherals]][[Category:Network]][[Category:Communication Software]] [[Category:Serial_interfaces]][[Category:Amstrad Products]][[Category:Expansion ROM]]
