ECLair

From Hackstrich
Revision as of 18:47, 16 December 2012 by SarahEmm (talk | contribs) (fixing a bunch of signals for which polarity was different in different places.)

ECLair is a long-term project to build an ECL minicomputer.

Project Status

  • 2012-12-15: Found bug in the datasheet of the MC10H181, fixed it and now the ALU checks out completely. Started integrating it into the CPU. Next step is to finish the MDR-XY data path so that Load Immediate instruction can be implemented, then Add can be implemented/tested.
  • 2012-12-14: Verilog transcription of ALU almost complete, but malfunctioning in the carry logic of the second bit. Will be using MC10H181 w/ MC10H179 CLA generator.
  • 2012-12-09: Started working on ALU design/verilog transcription.
  • 2012-12-08: Added decode support for ROM/RAM/device memory, got everything working so that now an instruction is fetched from ROM at startup and is jumped to in microcode. Started work on the X/Y registers, and started work on a microcode generator so I can stop typing in individual bits.
  • 2012-12-05: Got the part that's been diagrammed into Verilog and working. Now fetches instructions (from a constant right now, not RAM yet) and does jumps to their location in microcode.
  • 2012-12-04: Started the logical diagram and the microcode layout.
  • 2012-12-01/02: Spent the weekend reading Bit-Slice Microprocessor Design.
  • 2012-11-24: Basic ideas/architecture starting to get put together.

Architecture Overview

  • MECL-based (tentatively 10KH levels/speeds)
  • 25MHz main clock
  • 8-bit data width
  • 24-bit physical address, 16-bit virtual address
  • DMA support (at least for front panel, maybe one other DMA channel?)
  • Microcoded, running control store in SRAM for speed
    • Unless I can find equally-fast EPROMs
    • Copied to SRAM from EPROM before the system releases reset on powerup

Memory Map

  • 24bit / 16MB address space
  • 14MB for RAM, 1MB for ROM, 1MB for memory-mapped devices
  • 0x000000 - 0xEFFFFF - ROM
  • 0x100000 - 0x0FFFFF - RAM
  • 0x200000 - 0x1FFFFF - RAM
  • 0x300000 - 0x2FFFFF - RAM
  • 0x400000 - 0x3FFFFF - RAM
  • 0x500000 - 0x4FFFFF - RAM
  • 0x600000 - 0x5FFFFF - RAM
  • 0x700000 - 0x6FFFFF - RAM
  • 0x800000 - 0x7FFFFF - RAM
  • 0x900000 - 0x8FFFFF - RAM
  • 0xA00000 - 0x9FFFFF - RAM
  • 0xB00000 - 0xAFFFFF - RAM
  • 0xC00000 - 0xBFFFFF - RAM
  • 0xD00000 - 0xCFFFFF - RAM
  • 0xE00000 - 0xDFFFFF - RAM
  • 0xF00000 - 0xFFFFFF - Devices

Microcode Layout

Bit # Width Function Details
0 1 MC Addr Source low = IR, high = microcode bits
1 1 Jump MC Addr Microcode sequencer load
2-9 8 MC Jump Address Used if bit 0 = low
10 1 MAR Source low = Z, high = PC
11 1 MDR Source low = Z, high = data bus
12 1 MDR Load Low Byte Latches data or Z (determined by bit 11) into low byte of MDR
13 1 MAR Load MAR latch load (source specified by bit 10)
14 1 IR Load IR latch load from data bus
15 1 PC Increment Increment PC by 1
16 1 PC Load PC counter load from Z
17-19 3 Register Load from Z 000 - None
001 - A
010 - B
011 - C
100 - D
101 - SP
20 1 ALU Mode 0 = Arithmetic, 1 = Logic
21-24 4 ALU Operation 1111 - Z=X
25 1 MDR Load High Byte Latches data or Z (determined by bit 11) into high byte of MDR
26-28 3 X/Y Register Source 000 - Immediate Zero
001 - A
010 - B
011 - C
100 - D
101 - SP
110 - MAR
111 - MDR
29 1 RAM Read
30 1 RAM Write
31 1 X Load
32 1 Y Load
33 1 Z Load