Forgotten (Legacy) Microcontrollers from Yesteryear !

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Forgotten (Legacy) Microcontrollers from Yesteryear !

Post by lezanderson » 08 Feb 2020 12:34

Forgotten , Legacy Micro controllers from yesteryear 

A long long time ago when Dinosaurs Roamed the earth and you could afford to buy a brand new house at a reasonable price, then these microcontrollers (MCUs) were quite popular.Now most are forgotten,but they are still useful to the DIY Homebrew builder.

The Philips SCC68070 

The 68070 is basically a 68000 core put into a microcontroller with some memory mapped peripheral ICs on-chip.It can theoretically access 16Mb of Memory (ROM/RAM).  It (SCC68070) is a Philips Semiconductors-branded, Motorola 68000-based 16/32-bit processor produced under license. While marketed externally as a high-performance microcontroller, it has been almost exclusively used combined with the Philips SCC66470 VSC (Video- and Systems Controller) in the Philips CD-i interactive entertainment product line.Additions to the Motorola 68000 core include:Operation from 4 - 17.5 MHzInclusion of a minimal, segmented MMU supporting up to 16 MB of memoryBuilt-in DMA controllerI²C bus controllerUART16-bit counter/timer unit2 match/count/capture registers allowing the implementation of a pulse generator, event counter or reference timerClock generatorDifferences from the Motorola 68000 core include these:Instruction execution timing is completely differentInterrupt handling has been simplifiedThe SCC68070 has MC68010 style bus-error recovery. They are not compatible, so exception error processing is different.The SCC68070 lacks a dedicated address generation unit (AGU), so operations requiring address calculation run slower due to contention with the shared ALU. This means that most instructions take more cycles to execute, for some instructions significantly more, than a 68000.The MMU is not compatible with the Motorola 68451 or any other "standard" Motorola MMU, so operating system code dealing with memory protection and address translation is not generally portable. Enabling the MMU also cost a wait state on each memory access.While the SCC68070 is mostly binary compatible with the Motorola 68000, there is no equivalent chip in the Motorola 680x0 series. In particular, the SCC68070 is not a follow-on to the Motorola 68060.Even though the SCC68070 is a 32-bit processor internally, it has a 24-bit address bus, giving it a theoretical 16MB maximum RAM. However, this is not possible, as all of the on-board peripherals are mapped internally.68000 Microcontroller : ideal for designing an minimal 68000 system.
 * Note the SCC68070 is not 100% compatible with the original  Motorola MC68000, and it's not a follow-up to the 68060.

V25 uPD70320 the 8088 Microcontroller

uPD70320 /D70320 (8088 Micro controller ) NEC V2 was the microcontroller version of the NEC V20 processor. Features included:NEC V20 core: 8-bit external data path, 20-bit address busTimersInternal interrupt controllerDual-channel UART and baud rate generator for serial communications[1]It was officially phased out by NEC in early 2003Intel 8088 Microcontroler ( The NEC   V25) Ideal for designing a 'Mini' PC.

Zilog Z8 Encore RISC MCU
The Zilog Z8 is a microcontroller architecture, originally introduced in 1979, which today also includes the Z8 Encore!, eZ8 Encore!,[1] eZ8 Encore! XP, and eZ8 Encore! MC families.Signifying features of the architecture are up to 4,096 fast on-chip registers which may be used as accumulators, pointers, or as ordinary RAM. A 16-bit address space for between 1 KB and 64 KB of either OTP ROM or flash memory are used to store code and constants, and there is also a second 16-bit address space which may be used for large applications.On chip peripherals include A/D converters, SPI and I²C channels, IrDA encoders/decoders etc. There are versions with from 8 up to 80 pins, housed in PDIP, MLF, SSOP, SOIC and LQFP packages. The eZ8 Encore! series can be programmed and debugged through a single pin serial interface.The basic architecture, a modified (non-strict) Harvard architecture, is technically very different from the Zilog Z80. Despite this, the instruction set and assembly syntax are quite similar to other Zilog processors: Load/store operations uses the same LD mnemonic (no MOV or MOVEs), typifying instructions such as DJNZ, are the same, and so on.An IDE named Zilog Developer's Studio (ZDS) can be downloaded from Zilog's website including an assembler. The edition of ZDS II targeting Z8 Encore! and newer derivatives also includes a free compiler claiming ANSI C89 compliance.Primary competitors include the somewhat similar[2] Microchip PIC family, and all the Intel 8051 descendants. Also more traditional "von Neumann based" single chip microcontrollers may be regarded as competitors, such as the 6800/6809 based Motorola 68HC11, the Hitachi H8 family, and Z80-derivatives, such as Toshiba TLCS-870, to name just a few. Z88C0020 General purpose MCU
Z88C0020 DIP  Microcontroller  see:!

Intel 8051 Series MCUs
8051 Intel MCS-5 (commonly termed 8051) is a single chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems. The architect of the instruction set of the Intel MCS-51 was John H. Wharton.[1][2] Intel's original versions were popular in the 1980s and early 1990s and enhanced binary compatible derivatives remain popular today. It is an example of a complex instruction set computer, and has separate memory spaces for program instructions and data.Intel's original MCS-51 family was developed using N-type metal-oxide-semiconductor (NMOS) technology like its predecessor Intel MCS-48, but later versions, identified by a letter C in their name (e.g., 80C51) used complementary metal–oxide–semiconductor (CMOS) technology and consume less power than their NMOS predecessors. This made them more suitable for battery-powered devices.The family was continued in 1996 with the enhanced 8-bit MCS-151 and the 8/16/32-bit MCS-251 family of binary compatible microcontrollers.[3] While Intel no longer manufactures the MCS-51, MCS-151 and MCS-251 family, enhanced binary compatible derivatives made by numerous vendors remain popular today. Some derivatives integrate a digital signal processor (DSP). Beyond these physical devices, several companies also offer MCS-51 derivatives as IP cores for use in field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC) designs.
80C91  MCU:  AT89C51s and Similar MCU in DIP : See ... ed_on_8051

Posts: 181
Joined: 14 Aug 2012 15:31

Re: Forgotten (Legacy) Microcontrollers from Yesteryear !

Post by lezanderson » 14 Feb 2020 12:06

  • Designing your own Homebrew Mini PC with the D70320 (V25) MCU.

Firstly the D70320 is an enhanced 8088 based micro comptroller (MCU). Using a D70320 as the CORE to a homebrew ‘Mini’ PC will significantly simply the design. Eliminating the needs for several of the usual peripheral chips (DMA,PIC,PIT). A design example is below.

Design specification:

8088 (D70320) CPU as in original PC
DMA,PIT,PIC on D70320
8255 PIO I/9 Chip
8251 SIO I/O Chip
8087 Maths FPU
640K SRAM in 128K chunks
75HC138 (3 to 8 decoder) Memory decoder
74HC154 (4 to 16 decoder) I/O Decoder
6845 (V6366) for graphics (640,200,320x200 2,4,,16 colours) with 64K DRAM.
SN75489,SAA1099,YM3812 Sound chips ?
8477 Floppy disk controller. (upd765+Data Separator on one chip!)
12V input regulated to +5V

Central processor would be the D70320 (a 8088 , a derivative of the 8086 with auxiliary chips DMA,PIT,PIC). The 8088 was used in the original IBM 5150 PC

Input & output : Parallel and Serial chips 8255,8251 respectfully.

Memory decoding by a simple 74HC138 4 to 8 decoder . This would give memory in 128K chunks of RAM or ROM. 5 pieces of 128K SRAM would give 640K .

Input & output decoding would be done using say a GAL or a 74HC154 4 to 16 decoder. I/O mapping in accordance with original PC I/O Map.

Video would be achieved by using a V6366 which was used in the PC compatible Hercules Graphics card. Giving 64K VRAM and CGA type graphics nodes. 640x200 pixels, 320x200 pixels etc. with various (2, 4, 16 ) colours .

Sound could be achieved by a number of chips which were used in early PCs. SN76489, SAA1099 or the YM3812 (OPL2 Chip) some of these were used on early sound blaster cards.

Floppy Disks could be interfaced (implemented) using a 8477 advanced Floppy disc controller (internally a upd765 + Data Separator) for compatibility with original PC.

Hard Drive could be interfaced using a PIO Chip to a PATA Harddrive

USB Keyboard could be added via a generic USB keyboard adaptor.

7805 and 7812 Voltage regulators for +5V and +12V.

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