====== Z80 Rev0 Mezzanine Board for EPM240 Dev Board ======

**Note, Rev0 of Z80 Mezzanine board is superceded by [[:builderpages:plasmo:epm240dev:3vz80:3vz80rev1_1|rev1.1 of 3V Z80]] Mezzanine board**

===== Introduction =====

While Z80 is specified for 5V operation, selected CMOS Z80 are capable of running at 3.3V. This mezzanine board hosts such Z80 plus a 512K RAM and plugs on top of the EPM240 development board. The two-board Z80 computer can run RomWBW.

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=dbc4fb&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/dsc_77000531.jpg|{{https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/dsc_77000531.jpg?direct&600x314|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_epm240dev_3vz80_dsc_77000531.jpg}}]]

===== Features =====

  * CMOS Z80 selected for 3.3V operation
  * 512K RAM
  * 512 byte flash embedded in EPM240 can boot RomWBW
  * ACIA emulation in EPM240
  * SD card interface
  * RTC module based on DS1302
  * I2C interface
  * RomWBW capable

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=0a675c&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/3vz80_romwbw_annotated.jpg|{{https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/3vz80_romwbw_annotated.jpg?direct&400x267|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_epm240dev_3vz80_3vz80_romwbw_annotated.jpg}}]]

===== Theory of Operation =====

Boot from embedded 512-byte flash, etc, etc…place holder.

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=7d2f6e&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/bootsd_romwbw.jpg|{{https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/epm240dev/3vz80/bootsd_romwbw.jpg?direct&400x539|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_epm240dev_3vz80_bootsd_romwbw.jpg}}]]

===== Design Files =====

{{:builderpages:plasmo:epm240dev:3vz80:3vz80_rev0_scm.pdf|Schematic}}

{{:builderpages:plasmo:epm240dev:3vz80:3vz80rev0_pcb_gerber.zip|Gerber photoplot}}  files

{{:builderpages:plasmo:epm240dev:3vz80:3vz80_rev0_cpld_v1sd_bootromwbw_release.zip|EPM240 design files}}

  * {{:builderpages:plasmo:epm240dev:3vz80:v1sd_bootromwbw_release.zip|RomWBW SD bootstrap code}}  resided in EP240's embedded flash

EPM240 {{:builderpages:plasmo:epm240dev:3vz80:v1sd_bootromwbw_fast_noramdisk.zip|design files with fast SD bootstrap}}  (6 seconds), but no RAM disk at drive A

{{:builderpages:plasmo:epm240dev:3vz80:3vz80_rev0_bom.pdf|Bill of Materials}}

==== Software ====

{{:builderpages:plasmo:epm240dev:3vz80:3vz80_rev0_romwbw_sd_image.zip|RomWBW image}}  for 3VZ80. The RomWBW will be booted at power up. It takes 23 seconds to load and boot RomWBW from reset.