Changes

[[Amstrad]] released == The two [[RS232]] interfaces, both using the same input/output addresses - and, ultimately, therefore establishing the standard for serial interfaces - but with significantly different hardware.Amstrad Interfaces ==

== Original [[Amstrad]] released two [[RS232]] interfaces, both using the same input/output addresses - and, ultimately, therefore establishing the standard for serial interface ==interfaces.

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.

=== Pace serial interface (1986) ===

As a result, Amstrad dropped their original design and instead chose to remanufacture a [[PacePACE]] design. This included significantly 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 was a ROM version of Pace's the [[Commstar]] terminal utility, from [[CommstarHoneySoft]]. This was a user-friendly program with standard [[XModem]] 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 interface, this forced the use of software rather than hardware scrolling, making the interface unusable for terminal emulation at any speed above 2400 baud. The Amstrad/Pace version was announced on [[:File:ACU8612006.jpg|Amstrad Computer User, Dec 1986, page 6]]. A review occured in Amstrad Computer User, April 1987, pages 46 and 47.

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)

== Alternative software CP/M ==

The limitations of the Commstar softwareI/O ports are directly supported under CP/M (without needing additional drivers). Like many CP/M functions, and the desire to use more recently developed file transfer protocols functions are located in the AMSDOS ROM (such as [[XModem]]-1k, [[YModem]] and [[ZModem]]not on the CP/M disc) meant that many users chose to use their Amstrad serial interface . These functions are using hardcoded RAM addresses, which conflict with third-party softwarethe BASIC memory map, so they can be used only under CP/M, not under BASIC. This included:

A vast range The limitations of comms software was available for the [[CP/MCommstar]]software, including and the desire to use more recently developed file transfer protocols (such as [[Bulletin board|bulletin boardXModem]] hosts-1k, offline readers (notably [[CRRYModem]] - 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 [[UARTZModem]] chip (really???), which was reliable up meant that many users chose 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 use their Amstrad serial interface for the PCW) also includes some CPC informationwith third-party software. 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 Linkt to Article on Wikipedia about the 8250 UART used in the interface] == Manual == [[Original Amstrad RS232 interface|Manual of the original RS232 by Amstrad (OCR)]]

<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

Below shows schematic and pictures for the CPS8256 Serial Interface (for the Amstrad PCW, aka Schneider Joyce), ie. it is ''not'' really CPC hardware, however, the CPC interface should use a similar design (the major difference is probably that the CPC version contains a BIOS ROM, but no Centronics port). Credits: The gif and jpg's are from [http://www.z80.eu [http://cps8256.html www.z80.eu].

File:Cps8256-circuit.gif|CircuitSchematicFile:Cps8256-case-lower.jpg|Case top-viewlower sideFile:Cps8256-case-upper.jpg|Case bottom-viewupper side

[[Category:HardwarePeripherals]] [[Category:PeripheralsNetwork]][[Category:Communication Software]] [[Category:Serial_interfaces]][[Category:Amstrad Products]][[Category:Expansion ROM]]