Changes

== Intro == This interface was originally described in the book "[[Maschinenspracheprogramme und Hardware-Erweiterungen für Schneider CPC's]]" written by [[Paul Bauriedl]], released by IDEA Verlag in 1987. Around mid-nineties, it was turned into a single package and circulated in the internet. 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 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) <gallery>Image:SchneiderSioManualPage2.jpg|Schneider's Schematic (1985)Image:NoPicture.png|Paul Bauriedl's Schematic (1987)Image:Tim Riemann RS232.gif|Z80 STI Schematic (1996)</gallery> == How to build a RS232 - Interface for the CPC-Series!==- === Schematic and source code.===

WARRANTY: There is no warranty of any defects of your CPC!!! On my CPC everything works fine '''Bugs and I hope that you wonConfusing things in the GIF schematic:'t have any problems with this RS232''* Confusing: Signals 0..15 on the left side of the schematic refer to address lines A0..A15* Bug: Z80-InterfaceSTI Pin 3 (TCO) should be wired to Pin 39 (RC), not to Pin 34 (A1).

Second part: How to program the interface. (The assembler code is saved in RS232.ASM)

Z80-STI: 50 to 19200 bps (5,6,7 or 8 bit, 1, 1 1/2, 2 stopb.stopbits, all parity flags) 24 registers, use 16 registers (direct) with F8E0-F8EF, the last 8 registers can be used indirect with a special register

== The meaning and the adresses Addresses of the registers:==

register === Register 0, port adress F8E0:(Port F8E0h) Indirect Data ===

register === Register 1, port adress F8E1:(Port F8E1h) Handshake signals ===This register transfer transfers the data from and to the I/O port of the chip. If youuse V24 you can request handshake signals from this port. In this interfacethe following bits have this meaning: Bit 0: DTR (Data Terminal Ready) Bit 1: RTS (Ready to Send) Bit 2: CTS (Clear to Send) Bit 3: DSR (Data Set Ready) Bit 4-7: not used

register === Register 2-7, port adress F8E2(Port F8E2h-F8E7:F8E7h) Interrupt related ===

register === Register 8, port F8E8:(Port F8E8h) Indirect Index ===Bit 3-7 are used by the interrupt handler. With bit 0-2 you can choose theindirect register.

register === Register 9, port adress F8E9:(Port F8E9h) Timer Controls ===Controll Control register for timer A and B. You needn't to use the timer for a V24interface.

register === Register 10, port adress F8EA:(Port F8EAh) Timer B ===

register === Register 11, port adress F8EB:(Port F8EBh) Timer A===

register === Register 12, port adress F8EC:(Port F8ECh) Mode Control ===

  Bit 7 6 5 4 3 2 1 0

register === Register 13, port adress F8ED:(Port F8EDh) Rx Status ===

Bit 0: Receiver-Enable, set to 1 if receiving is possible.Bit 1: Memory full "1" or not "0". === Register 14 (If 8 Bits are received then the interface send memory fullPort F8EEh). register 14, port adress F8EE:Tx Status ===

Bit 0: Sending-Enable, must set to "1" if sending is allowed.Bit 7: Memory full "1" or not "0". This bit can be used to ask if a word is send or not. register === Register 15, port adress F8EF:(Port F8EFh) Rx/Tx Data ===

== Indirect registers (Choose them with register 8):==

For more exact informations please write to Mostek and ask for support for theZ80-STI. You also can look at the assembler code.

 == About the assambler assembler code:=========================

'''|FORMAT''', number of bps, number of stop-bits, data bits, parity on/off, parity even/odd Number of bps: 0 = 50 bps 1 = 75 bps 2 = 110 bps 3 = 150 bps 4 = 300 bps 5 = 600 bps 6 = 1200 bps 7 = 2400 bps Number of stop bits: 1 = 1 stop bit0 = 2 stop bit Data bits: 0 = 7 data bits1 = 8 data bits Parity: 1 = even0 = odd Parity: 1 = on0 = off Normally, you use 8N1 for connection with BBS's you can initialise this with|FORMAT, number of bps, 1, 1, 0, 1.  |RECORD, @a$The incoming chars will be read in a string. Control codes will be send to thestring, too, because sometimes you need it for binary transmissions.  |SEND, @a$The string is send until it ends, except you press ESC. The program will notsend CR or LF, so you can use this for binary transmission.

This interface is described in the book "Maschinenspracheprogramm und Hardware-erweiterungen fuer Schneider CPC's" from the IDEA Verlag. I hope that every''|RECORD, @a$''' -thing is ok with The incoming chars will be read in a string. Control codes will be send to the circuit plans and that string, too, because sometimes you don't have a broken CPC whenyou use need it ;-)for binary transmissions.

Sorry for bad english'''|SEND, @a$''' - The string is send until it ends, except you press ESC. (Please help me to find my faults)The program will not send CR or LF, so you can use this for binary transmission.

Tim Riemann* 1x [[Media:Mostek_3801_Data.pdf|Z80-STI (MK3801-4)]]Gartenweg 3* 1x SN75189 - RS232 to TTL level shifter35114 Haina* 1x SN75188 -KlosterTTL to RS232 level shifterGermany* 1x 74LS30 - Single 8-input NAND gateeMail: TCS* 1x 74LS138 -Software@t1-onlineof-8 inverting decoder/demultiplexer* 1x 74LS20 - Dual 4-input NAND gates* 1x 74LS04 - Hex Inverters* 1x 74LS32 - Quad 2-input OR gates* 1x 25pin SUB-D connector (male)* 1x connector for the [[Connector:Expansion_port|expansion port]]Note: The 74LS20, 74LS04, 74LS32 are the smaller logic symbols in the schematic.de

Third partNote 2: Used components:===========The 74LS138 splits the address space to four regions (which is total nonsense), the 74LS20 is then merging them back to a single region (which is undoing that nonsense). Although the 74LS138 is rather useless in this case, the book from Paul Bauriedl contains further schematics, in which the 74LS138 does have some purpose.

[[httpCategory://www.cpcwiki.eu/index.php/File:Rs232cpc.lzhPeripherals]] - All info and files on topic