====== MB020, A 68020-based Motherboard ======

===== Introduction =====

MB020 is a 4“x4” 68020-based motherboard with 3 RC2014 expansion slots. It allows RC2014 users to reuse their existing hardware to explore the 68020 processor.

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=8ab640&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/mb020/dsc_56340214.jpg|{{https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/mb020/dsc_56340214.jpg?direct&600x560|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_mb020_dsc_56340214.jpg}}]]

===== Features =====

  * MC68020
  * 4/16 meg 72-pin SIMM DRAM
  * 66.67Hz (14.7456MHz clock) level 1 autovector interrupt
  * Three RC2014 expansion slots

===== Functions =====

MB020 consists of a 4"x4" motherboard populated with 68020, EPM7128S, SIMM72 socket and 3 RC2014 expansion slots. The purpose is to reuse the existing RC2014 boards to explore MC68020. To that end, the boot ROM, I/O, mass storage will be the existing RC2014 boards. A 68020 monitor will be developed for the boot ROM so it can load files, display & modify memory and registers, and run applications. The I/O can be RC2014 SIO2 or 68B50 boards and a RC2014 CF board can be added to run CP/M68K.

===== Design Info =====

{{:builderpages:plasmo:mb020:mb020_scm_rev0.pdf|Schematic}}

Gerber {{:builderpages:plasmo:mb020:mb020_rev1.zip|photoplots, 4-layer pc board}}

<del>Gerber {{:builderpages:plasmo:mb020:mb020_r0.zip|photoplots}}  </del>{{:builderpages:plasmo:mb020:mb020_rev1.zip|mb020_r1.zip}}  <- 2-layer PCB is unreliable, replaced by 4-layer pc board.

Bill of Materials

[[:builderpages:plasmo:mb020:ec_mb020_rev1|Engineering change]]. An enginnering change is required to connect CPLD's reset to 68020 reset.

{{:builderpages:plasmo:mb020:mb020_r0_cpld_release.zip|CPLD}}  design files

[[:builderpages:plasmo:mb020:mem_map|Memory map]]

===== Software Tools =====

{{:builderpages:plasmo:mb020:ide68k_v3_3.zip|IDE68K ver 3.3}}

===== Example Configurations =====

Karlab's [[:builderpages:plasmo:mb020:configuration_a:cofiga_home|8K ROM, ACIA, and CF]].

[[:builderpages:plasmo:frr512k:rev0:mb020combo|FRR512K modified]] as a combination board of ROM/ACIA/CF for MB020

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