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/* Imported from Wayback Machine
   Original URL : https://retrobrewcomputers.org/doku.php?id=builderpages:plasmo:rr512k:rr512k_rev1
   Snapshot date: 2025-12-08
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*/

==== Table of Contents ====

[[#improved_512k_ram_rom_board_rev1|Improved 512K RAM ROM Board, Rev1]]

[[#introduction|Introduction]]

[[#features|Features]]

[[#design_information|Design Information]]

[[#software|Software]]

[[#jumper_configuration|Jumper Configuration]]

[[#applications|Applications]]

[[#eprom_programmer|EPROM Programmer]]

[[#i2c_interface|I2C Interface]]

[[#to_do|To Do]]

[[#rev11_wish_list|Rev1.1 wish list]]

====== Improved 512K RAM ROM Board, Rev1 ======

===== Introduction =====

Rev1 version simplifies the original design and uses all through-hole components for ease of assembly. It also added a oscillator so a functioning system can be built with a Z80 CPU board and a version 1 512K RAM/ROM board.

===== Features =====

Support ROMWBW

ROM emulation, with few jumper configurations, the ROM socket can be populated with RAM and data uploaded into the RAM via serial port at 115200 baud,

EPROM programmer, programming software can be loaded in RAM to program the EPROM,

A serial port emulating MC6850 ACIA, the same serial port used to load ROM image can be reuse as a regular serial port.

Spare capacities and I/O pins on CPLD for other user-defined functionalites.

Nominal speed is 14.7456MHz but can be overclocked to 22MHz

50mm x 102mm 2-layer pc board.

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=eb324e&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/rr512k/rr512k_rev1/dsc_60480926.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=600&h=273&tok=24a691&media=https%3A%2F%2Fwww.retrobrewcomputers.org%2Flib%2Fplugins%2Fckgedit%2Ffckeditor%2Fuserfiles%2Fimage%2Fbuilderpages%2Fplasmo%2Frr512k%2Frr512k_rev1%2Fdsc_60480926.jpg?600x273|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_rr512k_rr512k_rev1_dsc_60480926.jpg}}]]

===== Design Information =====

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:rr512k_rev1_scm.pdf|Schematic]]

Gerber [[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:rr512k_rev1_gerber.zip|photoplot]]

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:rr512k_rev1pcb_cpld_release_with_i2c.zip|CPLD equations]] ←updated CPLD with I2C interface

Bill of Materials

[[builderpages:plasmo:rr512k:rr512k_rev1:ec_i2c|Engineering change]] to enable I2C interface and CTS handshake

==== Software ====

ROMWBW, this board is designed to run Wayne Warthen's excellent ROMWBW. The binary of [[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:romwbw191_bin.zip|ROMWBW v1.9.1]] is provided here for convinience. The homepage for ROMWBW is located in [[https://github.com/wwarthen/RomWBW|GitHub]].

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:rrmon_v0_2_rr512k_rev1.zip|RRMon rev 0.2]], this is separate monitor for this board loaded via serial bootstrap software. Its purpose is board diagnostic. The monitor is under development and subject to changes.

==== Jumper Configuration ====

[[https://www.retrobrewcomputers.org/lib/exe/fetch.php?tok=af47cd&media=https://www.retrobrewcomputers.org/lib/plugins/ckgedit/fckeditor/userfiles/image/builderpages/plasmo/rr512k/rr512k_rev1/rr512k_r1_jumpers.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=400&h=256&tok=c7f07f&media=https%3A%2F%2Fwww.retrobrewcomputers.org%2Flib%2Fplugins%2Fckgedit%2Ffckeditor%2Fuserfiles%2Fimage%2Fbuilderpages%2Fplasmo%2Frr512k%2Frr512k_rev1%2Frr512k_r1_jumpers.jpg?400x256|www.retrobrewcomputers.org_lib_plugins_ckgedit_fckeditor_userfiles_image_builderpages_plasmo_rr512k_rr512k_rev1_rr512k_r1_jumpers.jpg}}]]

===== Applications =====

==== EPROM Programmer ====

By enable the serial bootstrap ROM on CPLD, the 512K RAM/ROM, in conjunction with a Z80 CPU board, can serve as a EPROM programmer. The following instruction is for programming SST39SF040 EPROM.

The jumper configuration of RR512K_rev1 is

T24 jumper to ground

T22 jumper to ground

T25 jumper to T27

T26 jumper to T28

Insert a SST39SF040 in the FLASH socket (U2),

Connect a serial port to connector P2 and set baud rate to 115200 N-8-1,

Power up the board and send the serial loader, [[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:serload_rr512k_rev1.zip|serload.bin]] to the serial port. serload.bin is a binary file so be sure to check the 'Binary' box,

The EPROM programmer will respond with:

//RR512K_Rev1 Loader v0.2 9/26/20\\
Auto start at 0xB400//

Next send the EPROM programmer, [[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:progsst39f040_rr512k_rev1.zip|progSST39F040.hex]]. The console will respond with:

//……………………………………UX//

//RR512K_rev1 Programmer for SST39SF040 ver 0.3 9/26/20\\
SST39SF040 will now be erased\\
Enter Y to proceed, all other keys to abort//

Enter 'Y' (upper case Y) to chip erase SST39SF040 EPROM or any other character to cancel the operation. Once chip is erased, the program will prompt user to send the image file in Intel Hex format: (as an example, this is [[https://retrobrewcomputers.org/lib/exe/fetch.php?media=builderpages:plasmo:rr512k:rr512k_rev1:romwbw191_hex.zip|ROMWBW version 1.9.1]] )

//SST39SF040 erased, ready to upload the image file\\
…………………………………………..// (truncated) //………………………….X//

Programming is completed when 'X' is output. It takes about 2 minutes to program 512K EPROM.

==== I2C Interface ====

[[builderpages:plasmo:rr512k:rr512k_rev1:ec_i2c|Engineering change]] to add 4-pin I2C connector to interface to 128×64 OLED display

===== To Do =====

Developing additional functions in CPLD utilizing the spare I/O pins:

SPI

WB2812B interface to drive array of RGB LEDs

==== Rev1.1 wish list ====

Add RTS handshake

Add IDE interface for disk-on-module

Move jumpers to more convenient locations

Add interface to I2C, SPI, and WB2812B

optional reset supervisor