The British Camputers Lynx Microcomputer

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lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

The British Camputers Lynx Microcomputer

Post by lezanderson » 11 Jun 2019 14:56

The British Camputers Lynx Microcomputer


What is a Camputers Lynx : The Camputers Lynx was a 1980s Z80 based British microcomputer . Lynx had similar hardware to the Amstrad CPC series but was completely incompatible, note the Lynx was released before the Amstrad CPC.

See Wiki page: https://en.wikipedia.org/wiki/Camputers_Lynx

See Old Computers : http://www.old-computers.com/museum/com ... c=158&st=1

The Basic specification of the Camputers Lynx is

Z80 CPU 4Mhz or on later models 6MHz
48K,96K,128K RAM max 192K ?
16K,24K ROM
6845 Video Chip giving several graphics modes, 256,224,512x224 etc
DAC (Digital to analogue converter) to give basic sound effects.
68B21 on early models for I/O , later models used TTL glue logic.
External PSU

lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

Re: The British Camputers Lynx Microcomputer

Post by lezanderson » 11 Jun 2019 14:59

Musings on Designing a Modern Camputers Lynx ?

Designing a Modern(ish) homebrew Camputers Lynx , isn’t so unrealistic or impractical as you may think, as all of the necessary original chips are still available.

Design specification:

Z80 CPU (Z84C0020xx) 20MHz Max
192K Fast SRAM (instead of old slow DRAMs)
64K Fast EEPROM
6845 Video Chip as in original (HD46505-x,UM6845,R6545 etc)
Z80 KIO multifunction I/O Chip
Intel 82C55 Parallel I/O Chip
Intel 82C51 Serial I/o Chip
68B21 or ‘Glue’ logic as in original unit.
EPM7128SLC84 CPLD as Glue logic
EPM7032SLC44 CPLD as Glue Logic
DAC for sound as in original Camputers Lynx
Real Time Clock (RTC)
Maths Co-Processor
Microcontroller for PS/2 keyboard (89C201 or similar)
Real Sound Chip : SAA1099,SN76489,YM2149 or similar ?
7805 Voltage Regulator 1.5A


CPU : Modern CMOS Z80 running Max 20MHz, Switchable between, 4Mhz,5Mhz,6Mhz,8MHz,10Mhz,12MHz,16MHz,20MHz, using external software controlled by glue logic or an Microcontroller (MCU) ?

User RAM : 192K this could be three banks of 64K UM61512-15 fast 15ns SRAM or a combination of Fast 128K IS61C1024-10 10ns SRAM + UM61512 SRAM or even IDT7008 64K Dual port SRAM. This would easily allow clock speeds of 20MHz operation

ROM: W27C512-45 45ns Fast EEPROM could be used instead of the old 8K Banks of slow EPROM as in the original. 45ns access time would allow 20Mhz Z80 clock speed.


Input / Output : I/O
The 68B21 was used to do quite a sizeable amount of the I/O on the original Lynx, these are still available and could be used. Or a blank CPLD/Glue logic could be programmed to do these function.

Z80 KIO. This multifunction chip has Serial ports, parallel ports, a Counter Timer etc al on one chip, as far as I know they only come in PLCC package ?

Intel 82C55 PIO , parallel port ideal for connecting a CF Card or PATA Hard Drive ?

Intel 82C51 SIO, giving even more serial I/O

Glue Logic (CPLDs)
The necessary glue logic to ‘Hold’ The system together could be programmed onto blank CPLDS like the ATF1508,EPM7128SLC84 etc. These have +3.3 Supply rail but can handle +5V I/O . This Keyboard matrix , printer interface etc could be put on these too.

PS/2 keyboard using a microcontroller (MCU)
A PS/2 keyboard could be interface using a modern or even legacy MCU such as the 89C2051, 89C51 etc

Video Chip / Video Logic (MC6845)
The video logic , based around a 6845 or clone would be used as these are readily available and still cheap. It could even be connected to a Dual Port SRAM (such as IDT7008 64K x 8 35ns) as not to slow the CPU down . As the 6845 in the original HALTS the Z80 CPU to draw it’s Raster Display. This would increase the performance by at least 30%.
Or it could be connected to fast SRAM such as UM61512, rather than slow DRAM. This would mean some ‘Interface / Glue’ logic would be needed between the 6845 and SRAM or Dual Port SRAM.

Sound Output.
The original unit used a rather simple and crude DAC to produce simple sound effect. This was quite common back in the 80s, the Dragon & ZX Spectrum did a similar thing, probably due to greed !
However there are plenty of cheap and readily available legacy sound chips (Programmable Sound Generators PSGs). These include PSGs like the YM2148 (AY-3-8910),SAA1099,SN76489 etc.

Real Time Clock (RTC)
A Real time Clock RTC , such as a DS12887,DS12885 would give, TIME,DATE,YEAR etc. This would be useful, though not used in the original Lynx.

Floppy disk controller (FDC)
Floppy disk are rather obsolete, but you could use a chip like the WD177x (MB8877A) used in the BBC Micro and many other. Or a upd765 +SED9420 ( 8477 , PC8477BC-1 ) This would allow legacy floppy drives to be accessed.

Maths Co-Processor
A Maths Co-Processor such as a AM9511 could be used,thought this may be of limited usefulness ? An AM9511 is supposed to run 8 times faster than the equivalent maths software routines

Power Supply +5V
As all modern legacy chips only need a +5V supply there’s is no need for +12V and -5V as there was back in the early 80s. Thus a +12V 2A DC regulated input could be turned into a +5V (Regulated) and +12V supply for the Motherboard. This would do the job !


Rough Design Examples :


Basic (simplistic) Design 1
Z80 CPU DIP40 (running at 6Mhz)
128K SRAM 70ns DIP32
32K EPROM 70ns DIP28
68B21 PIA I/O Chip DIP40
6845 CRTC (Video Chip)
PSG (Sound Chip) YM2149 etc DIP40
DS12885 RTC DIP
Glue Logic (GAL/CPLD etc)
DAC for Sound output BEEPS etc
7805 Regulator

This design would be very similar to the original just using more modern, SRAM, EPROM and glue logic.

Design 2 :
Z80 CPU DIP40 (running at switchable 5Mhz,10Mh,6MHz,12MHz)
128K SRAM 70ns DIP32
32K EPROM 70ns DIP28
68B21 PIA I/O Chip DIP40
Intel 82C55 DIP40 PIO
Intel 82C51 DIP SIO
6845 CRTC (Video Chip)
89C201 MCU for PS/2 keyboard
PSG (Sound Chip) YM2149 etc DIP40
DS12885 RTC DIP
AM9511 Maths Processor DIP
Glue Logic (GAL/CPLD etc)
DAC for Sound output BEEPS etc
upd765 + SED9420 Floppy disc controllers.
7805 Regulator


Design 3: PLCC
Z84C0020VEC 20MHz Z80 PLCC44
Z84C9012xxx 12MHz Z80 KIO PLCC
192K Fast SRAM (3x UM61512-15 ) SDIP32
64K Fast EEPROM (W27C512-45) PLCC32
Intel 82C55 PLCC44 PIO
Intel 82C51 PLCC SIO
Glue Logic (CPLDs,GALs etc.) PLCC
6845 CRTC (Video Chip) DIP40
Sound Chip/Chips (SAA1099,SN76489,YM2149 etc) DIP
DS12885Q PLCC RTC
MCU for PS/2 Keyboard DIP/PLCC
PC8477BV-1 Advanced FDC (Floppy Disk Controller) PLCC68
7805 +5V Regulator


Design 4 : PLCC with Dual Port SRAM
Z84C0020VEC 20MHz Z80 PLCC44
Z84C9012xxx 12MHz Z80 KIO PLCC
128K Fast SRAM IS61C1024-10 SDIP32
64K Dual Port SRAM (IDT7008-xx PLCC) as User & Video RAM.
64K Fast EEPROM (W27C512-45) PLCC32
Intel 82C55 PLCC44 PIO
Intel 82C51 PLCC SIO
Glue Logic (CPLDs,GALs etc.) PLCC
6845 CRTC (Video Chip) DIP40
Sound Chip/Chips (SAA1099,SN76489,YM2149 etc) DIP
DS12885Q PLCC RTC
MCU for PS/2 Keyboard DIP/PLCC
PC8477BV-1 Advanced FDC (Floppy Disk Controller) PLCC68
7805 +5V Regulator


These are Very simplistic design concepts and would/will take a lot of skill and knowledge to make a working design. But they do give a good starting point for your own ideas.

lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

Re: The British Camputers Lynx Microcomputer

Post by lezanderson » 11 Jun 2019 15:03

Is Anyone design/building their own Camputers Lynx ?

If you are designing or building your own Camputers Lynx then I may have some old Z80 ICs and stuff you can have for Free !

Just email me at ; lezanderson@gmail.com

ICs ;

Z80 CPUs
Z80 KIOs
SRAM/EPROM and other memory chips
82C55 & 82C51 I/O Chips
CPLDs
Voltage Regulators
Sound Chips
Video Chips including MC6845, R6545, HD46505-2 etc
etc etc

lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

Re: The British Camputers Lynx Microcomputer

Post by lezanderson » 12 Jun 2019 11:37

Motorola 6845 CRTC (Cathrode Ray Television Controller)


The video chip used in the Camputers Lynx is the Motorola 6845
Video Chip or CTRC. See Wiki page : https://en.wikipedia.org/wiki/Video_display_controller
https://en.wikipedia.org/wiki/Motorola_6845

The 6845 is part of the 6800 IC set and designed to be used with the 6800 or 6502 CPUs. However it can be used with practically any CPU including the Z80.

The Z80 and the 6845 can’t use the same RAM at the same time . Thus the 6845 HALTs the Z80 CPU when drawing it’s raster display (i.e. draws the screen on your TV). This can slow the system down by 30%+.

See Wiki pages on how a TV screen works: https://en.wikipedia.org/wiki/Raster_scan
PAL TV system :https://en.wikipedia.org/wiki/PAL
NTSC TV System : https://en.wikipedia.org/wiki/NTSC


Using Dual Port SRAM
By using Dual Port SRAM the Video Chip 6845 nd Z80 CPU can both access RAM with out this problems of HALTing the CPU to draw the TV display. As Dual port SRAM like the IDT7007 (32kx8) are readily available, using them as User/Video ram is quite a good option, though it does add a little extra complexity to any design.

Using ‘Super Fast SRAM’ as D/Port SRAM.
By using super fast SRAMs (like UM61512 15ns, IS61C1024-10 10ns) and a CPLD as Glue logic a Fast SRAM can be used just like Dual Port SRAM. This would work by synchronising CPU and the Video Chip, Example in a 50ns access time 25ns would be for the Z80 CPU and 25ns for video Chip.


To see how a Analogue TV works and it's Raster display see: https://en.wikipedia.org/wiki/Analog_television

lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

Re: The British Camputers Lynx Microcomputer

Post by lezanderson » 17 Jun 2019 11:45

Costing a design

When designing any system from the outset an eye should be kept on projected costs. If this is not done you could end up designing something that is simply unrealistically expensive to make !

Costing a Basic Design:

(Design 1)
Z80 CPU 6MHZ (Z84C0006PEC) DIP 40 ………………..........….....$2.0
128K SRAM (HM628128 TC551001 or similar 70ns) DIP32….....$1.0
32K EPROM ( 27C256 )……………………………………............….…...$1.0
6845 CRTC Video Chip DIP40………………………….......…….….....$3.50
6521 PIA Chip for I/O DIP40…………………………….......…….….....$2.0
CPLD PLCC84 (EPM7128SLC84,ATF1508 etc)……....……….…..….$2.0
Sound Chip (SN76489,YM2149 etc)……………………......……..…….$1.0
DAC for simple sound effects…………………………….....….….……..$1.0
PAL TV Encoder DIP……………………………………………...........…...$2.0
Miscellaneous ICs…………………………………………………..............$3.50
7805 Regulator……………………………………………………...........….$0.10

Total Cost for ICs <$20.00

Based on $20.00 for ICs, $20.0 to get a PCB make, and $20.0 for other miscellaneous items, resistors, capacitors, switches, connectors etc. Then the Total build cost should be <$60.00 or about £45.00.

Note when sourcing ICs, always test them as soon as you get delivery. This includes , NOS (New Old Stock), Brand New and Pulls. Avoid CPLDs and PLDs that are Pulls as they are already programmed and you may not be able to erase and reprogram them ! Best to stick to Brand New or NOS CPLDs/GALs/PLDs. Also read the datasheets before buying to source the right ICs especially things like programmable logic as some CPLDs need expensive programmers to program them !


*********************************************************

(Design 2, Extended Basic design)
Z80 CPU 6MHZ (Z84C0006PEC) DIP 40 …………………..…............$2.0
128K SRAM (HM628128 TC551001 or similar 70ns) DIP32….....$1.0
32K EPROM ( 27C256 )……………………………………….…...............$1.0
6845 CRTC Video Chip DIP40……………………………….........…....$3.50
6521 PIA Chip for I/O DIP40……………………………….......…..…....$2.0
CPLD PLCC84 (EPM7128SLC84,ATF1508 etc)……....……….….….$2.0
Sound Chip (SN76489,YM2149 etc)……………..……….....…….…….$1.0
DAC for simple sound effects……………………..………....….………..$1.0
PAL TV Encoder DIP…………………………………..……….........……...$2.0
Miscellaneous Ics……………………………………..……….…........….....$3.50
7805 Regulator………………………………………...……….........…….….$0.10
Plus
8255 Intel PIO for parallel I/O (to connect PATA Harddrive etc)....……$1.0
82C51 Intel SIO for Serial I/O……………………………….............……....…..$1.0
DS12885 Real Time Clock DIP…………………………….….............……......$1.50
AM9511 Maths Co-Processor for Hardware Floating point maths...…..$3.50
Floppy Disc Controllers (upd765+SED9420, or WD1793 etc)…......……$5.0
Microcontroler (89C2051,89C51 etc) for PS/2 keyboard………….....….$1.0


Total cost for ICs is now approximately $32.00

Based on $32.00 for ICs, $23.0 to get a PCB make, and $20.0 for other miscellaneous items, resistors, capacitors, switches, connectors etc. Then the Total build cost should be <$75.00 or about £58.00.

*********************************************************


(Design 3: Advanced 20MHz Design)
Z80 CPU 20MHZ (Z84C0020VEC) PLCC44 ……………….…..…............$2.0
Z80 KIO 12MHz (Z8S9012Vxx) PLCC………………………......…….........$2.50
128K SRAM (2x UM61512-15 15ns) DIP32…….………………..............$3.0
64K EPROM ( W27C512 45ns ) PLCC32…………...……….….…...........$1.0
6845 CRTC Video Chip DIP40………………………………...…................$3.50
IDT7008 (Dual Port SRAM 64Kx8bit) PLCC68……..………..…........….$15.00
CPLD PLCC84 (EPM7128SLC84,ATF1508 etc)……………...…..........….$2.0
CPLD PLCC44 (EPM7032SLC44 or similar) …………………...........….….$2.0
GAL22V10 PLD PLCC package…………………………………….................$2.0
GAL16V8 PLD… PLCC package……………………......………….........…...$1.50
Sound Chip. (SN76489,YM2149,SAA1099 DIP (3 Chips….......….….….$4.0
Op-Amp (Mixer) for Sound Chips…………………………….............……..$1.0
DAC for simple sound effects……………………………….…...........……...$1.0
PAL TV Encoder DIP/PLCC………………………………………...................$2.0
8255 Intel PIO for parallel I/O (PATA Harddrive etc) PLCC44..…..…$1.0
82C51 Intel SIO for Serial I/O PLCC…………………………............……..$1.0
DS12885Q Real Time Clock PLCC……………………….….............……..$1.50
Floppy Disc Controller 8477 PLCC …………………………............……….$2.0
Microcontroler (89C2051,89C51 etc) for PS/2 keyboard………..….….$1.0
Miscellaneous ICs………………………………………………................….....$3.50
7805 Regulator……………………………………………..................………….$0.10

Note: CPLDs / PLDs / GALs would be blank and need to be programmed to emulate the necessary Glue logic to make the system work. This would include Memory management, I/O selection, interfacing the 6845 to the IDT7008 Dual Port SRAM etc.


Total cost for ICs approx. $50.00

Based on $50.00 for ICs, $30.0 to get a PCB make, and $20.0 for other miscellaneous items, resistors, capacitors, switches, connectors etc. Then the Total build cost should be approx. $100.00 or about £75.00 .


*********************************************************

lezanderson
Posts: 167
Joined: 14 Aug 2012 15:31

Re: The British Camputers Lynx Microcomputer

Post by lezanderson » 20 Jun 2019 12:04

Miscellaneous :



Motorola 6845 Display Controller (Video Chip)

Further Reading on the 6845 (and clones) [HD46505,6845,6545,V6366 etc]

Wiki : https://en.wikipedia.org/wiki/Motorola_6845

V6366 : http://www.vgamuseum.info/index.php/new ... a-v6366c-f

Hercules Graphics Card : https://en.wikipedia.org/wiki/Hercules_Graphics_Card

The R6545 is a later version of the 6845 with some new features. The V6366 is a later and more advanced version of the 6845.

*******************************************************************************************************

PS/2 Keyboard :

See for schematics and stuff on how to build a PS/" keyboard reader:

http://www.burtonsys.com/ps2_chapweske.htm

http://www.pyroelectro.com/tutorials/ps ... matic.html

https://hackaday.com/2009/09/29/connect ... ontroller/

https://www.pantechsolutions.net/interf ... ment-board

https://www.pantechsolutions.net/how-to ... ment-board

*********************************************************************************************************

Floppy Disc Controllers (FDCs)

See Wiki ; https://en.wikipedia.org/wiki/Floppy-disk_controller


The 8477 Advanced Disk Controller is a upd765+SED9420 all on one chip (PLCC68 etc)

See http://ohlandl.ipv7.net/floppy/DS011332.pdf

The upd765 was used in Spectrum +3, Amstrad CPC etc


WD177x (as used in BBC micro and others)

https://en.wikipedia.org/wiki/Western_Digital_FD1771

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