# MZ80A_RFS **Website:** [engineers@work](https://eaw.app) | **Repository:** [git.eaw.app/eaw/MZ80A_RFS](https://git.eaw.app/eaw/MZ80A_RFS) --- ## Overview
The Sharp MZ80A came with 48K RAM and 4K ROM and apart from the option to add a 2K User RAM/ROM and a 4K Floppy Drive ROM, there was no further possibility to expand the machine memory capabilities at the hardware level and thus no additional firmware could be added for use at power-on. Add-ons had to rely on loading control firmware into RAM via tape or floppy, thus depleting valuable application space. Some machines of the same era utilised a scheme called 'banking' whereby much larger memories would occupy a smaller block within the CPU address space and be selected according to features required and hardware attached. The BBC Micro was such a machine with up to 16 banks of 16Kb, it made the machine much more useable.

One of the separate projects I've been working on was a 40/80 Column switchable display and colour output. This upgrade requires different software, either a complete rewrite of the original monitor or a patched copy for 80 column mode. Wanting to keep the machine as original as possible, using a rewritten ROM is out of the question thus I would need 2 ROMS, original for 40Column and a patched one for 80Column.

Thus was born the need for Rom Paging in the Sharp MZ80A, ie. Use a modern Flash RAM to house multiple 4K Roms which can be *switched in* to the 4K Monitor ROM address space according to the hardware upgrade being used.

It was also seen when using large Flash RAM's that it was possible to store programs that would normally be present on tape or floppy and load at much higher speed making use of the computer that much easier.

This upgrade goes a bit further and uses the 4K Monitor ROM and 2K User ROM space to map in up to 4x512Kbyte Flash RAMs and/or 1x512Kbyte Static RAM which provides multiple paged roms (theoretical 1024 x 2K slots and 128 x 4K slots) and/or a paged RAM (256 x 2K slots) along with the required custom software to control the banking which I've termed the 'Rom Filing System'.
This document along with the [Rom Filing System](/sharpmz-upgrades-rfs) and [CP/M](/sharpmz-upgrades-cpm) document form the start of the Rom Disk documentation. Within this repository are the schematics, PCB Gerber files and the Gitea repository sub-modules implement the Rom Disk hardware, the Rom Filing System and CP/M software. -------------------------------------------------------------------------------------------------------- ### Rom Disk Hardware
It is quite easy to make upgrades for older tech these days by using one of the plethora of ready made development boards such as the Raspberry Pi or standalone microcontrollers such as the STM32 series and the rich libraries of ready made software.

I did consider using an STM32F series microcontroller as a ROM emulator as they have the price, performance and packaging advantages but then the goal of this project and the goals of the other Sharp MZ80A upgrades (excluding the tranZPUter) was to use old tech and keep the machine original.

Unlike a commercial project where part choice to provide the required functionality is imperative to keep costs low, with this project the focus is on the learning journey using parts such as the 74 series which were available at the time of the Sharp, excepting of course the larger Flash RAM and Static RAMs which came a few years later but necessary for the functionality.

The sub-sections below outline the hardware design and pcb, including all versions for comparison.
-------------------------------------------------------------------------------------------------------- ### v1.1 Combined Schematic ![image](../images/MZ80A_RFS_v1_1.png)
Version 1.1 of the Rom Disk was relatively simplistic, adding a 512K Flash RAM in each of the Monitor and User ROM sockets. A latch was added to select the correct 4K/2K page within the Flash RAM under program control.
#### v1.1 PCB

Version 1.0 PCB (which became v1.1 with minor changes). Originally I planned to use skinny dip memory devices but changed to PDIP and had to adapt the board accordingly.
![Assembled PCB](../images/IMG_9625.jpg) -------------------------------------------------------------------------------------------------------- ### v2.0
Version 2.0 took the developments of v1.1 and addressed the short comings, ie. more Flash RAM space required, addition of an SD Card and additional Static RAM.

The SD card started off as a bigbang development using a Sharp Parallel printer card, which enabled the software and basic framework to be developed. The design then went further by adding a hardware SPI circuit. The hardware circuit is almost as quick as the Flash RAM devices whereas the software SPI circuit is faster than a floppy disk but noticeably slower than ROM.

Having ported CP/M (by writing a custom CBIOS) to run under the Rom Filing System on the Rom Disk, I noticed the shortfalls in lack of RAM, where even with ROM banking I could only make 46K available to CP/M and programs such as the venerable Star Trek V2 failed to run. In order to address this issue an additional 512K RAM device was added which could be paged in 2K segments. This RAM would make available storage space for CP/M structures such as control blocks and variables in order to free up more space.

All the above came together as the v2.0 design and the schematics/pcb details are in the sub-section below.
### v2.0 Memory Schematic ![image](../images/MZ80A_RFS_v2_0a-2.png)
Version 2 of the hardware builds on the experiences learnt making version 1. It adds a coded latch (a programmable number of reads required in the 0xEFF8-0xEFFF region) in order to enable access to the control registers and I/O otherwise both read and write access is performed on memory. It also adds two additional (optional) memories for increased storage and RAM. The additional two devices can be both Flash RAM or 1 Flash RAM and 1 Static RAM. The Static RAM is to increase the capability of CP/M, such as number of SD drives available and the memory available to TPA applications.

The schematic has been split into two distinct functions, Memory and Control logic. Above is the new Memory schematic which retains the single 512K Flash RAM which replaces the Monitor ROM, write access is not possible as the underlying Sharp hardware blocks write on Monitor ROM select. In the User ROM socket are 3 devices, the 512K Flash RAM from version 1 but with write access and an additional 2 devices.
### v2.0 Control Logic Schematic ![image](../images/MZ80A_RFS_v2_0a-3.png)
The second schematic is the control logic. This creates the needed memory select lines from the main board in combination with address decoding and programmable latches for the upper address lines.

A coded latch is added (74HCT191) which only enables I/O when a read is made to the region 0xEFF8-0xEFFF for a programmable number of times. The latch U14 bits 5:3 control the number of read operations needed to active the 74HCT191. At start up U14 bits 5:3 will be 0 and to enable I/O you need to perform 16 read operations in the region 0xEFF8-0xEFFF to activate the 74HCT191 TC (terminal count) which in turn will enable the I/O control registers in the region, ie. 0xEFF8-0xEFFF. When the control registers are active the memory region 0xE800-0xEFF7 still accesses the selected Flash RAM/RAM device. A read from the location 0xEFF9 will reset the 74HCT191 and the control registers will be deactivated, the region 0xEFF8-0xEFFF now access the selected Flash RAM/RAM.

In addition it adds 2 SPI circuits, only one of which will be assembled on the PCB according to choice. The first is a software bitbang SPI using the Z80 to form the correct serial and clock signals in order to talk to an SD Card. This method uses few hardware components but is much slower. The second is a hardware SPI running at 8MHz which is capable of transferring/receiving a byte in less time that the Z80 takes to perform a read, this allows for performance similar to the Flash RAM storage.
#### v2.0 PCB

As per previous schematics and PCB boards, this project has been designed with KiCad Schematic Capture and PCB Layout. Below are the finished boards awaiting components and assembly.
![PCB TopSide](../images/RFS_v2_PCB_TopSide.jpg) ![PCB UnderSide](../images/RFS_V2_PCB_UnderSide.jpg) ![Assembled PCB](../images/IMG_1242.jpg) -------------------------------------------------------------------------------------------------------- ### v2.1
Version 2.1 is a tidy up and bug fix version. In version 2.0 I noticed an error (due to the Sharp MZ decoder always creating User ROM Chip Select pulses even when not addressing the User ROM, this was determined to be the refresh address logic decode) and it interfered with the control latch reset. I thus added a wire AND gate and changed the select line which reset the coded latch.

The chance was also taken to tidy up the PCB silk screen to orient the markings as per the Sharp MZ motherboard and can be seen in the sub-section below.
### v2.1 Memory Schematic ![image](../images/MZ80A_RFS_v2_1-2.png)
Version 2.1 is a bug/shortcoming fix of v2.0. The circuit diagrams of v2.0 have already been updated with the changes but the physical board relied on component additions and wires. Hence this circuit is identical to v2.0 (in hindsight I should not have updated the v2.0 schematic but created v2.1 at the point of change).

Nothing has changed on the memory schematic between the original v2.0 and v2.1 designs.
### v2.1 Control Logic Schematic ![image](../images/MZ80A_RFS_v2_1-3.png)
The second schematic is the control logic. The changes made between v2.0 and v2.1 were the addtion of an and gate, created with diodes and the rewiring of 0xEFF9 as the coded latch clear signal.
#### v2.1 PCB

As per previous schematics and PCB boards, this project has been designed with KiCad Schematic Capture and PCB Layout. Below are the assembled PCB's along with installation in an MZ-80A.
![PCB TopSide](../images/RFS_v2.1_Topside.png) ![PCB UnderSide](../images/RFS_v2.1_Underside.png) ![Installation](../images/RFS_v2.1_Installation1.png) -------------------------------------------------------------------------------------------------------- ### Installation
Installing the Rom Disk requires opening the Sharp MZ-80A and locating the Monitor ROM and User ROM chips on the motherboard.
Steps:
  1. Power off the machine and disconnect the mains cable.
  2. Remove the two screws on the underside of the case and lift the top cover.
  3. Locate IC2 (Monitor ROM, 24-pin DIP near the Z80) and IC3 (User ROM, 24-pin DIP). Carefully remove both chips using a chip puller or flat-bladed screwdriver, levering from both ends equally to avoid bending pins.
  4. Insert the Rom Disk PCB — the two DIP lifter pin arrays plug directly into the vacated ROM sockets. Orient the board so the pin 1 markers align. Press firmly until fully seated.
  5. Route the SD card socket cable to an accessible position. Many builders use the existing CMT opening or cut a small slot in the rear panel.
  6. Close the case.
-------------------------------------------------------------------------------------------------------- ### Programming the Flash ROMs
The Flash ROM chips (SST39SF040, 512 KB each) must be programmed before installation. Pre-built ROM images are available in the releases/ directory of the RFS Gitea repository. A TL866 II+ or compatible programmer with the minipro utility is required.
| Image File | Flash Chip | Description | |------------|------------|-------------| | `MROM_ROMDISK_256.bin` | U1 (Monitor ROM socket) | Monitor ROM banks: SA-1510, 80-col SA-1510, CP/M CBIOS, RFS MROM utilities, 1Z-013A monitors, IPL | | `USER_ROM_256.bin` | U4 (User ROM socket, chip 1) | RFS banks 0–7, CP/M CBIOS banks 8–11, packed MZF applications | | `USER_ROM_II_256.bin` | U5 (User ROM socket, chip 2) | Additional MZF applications (optional) | | `USER_ROM_III_256.bin` | U6 (User ROM socket, chip 3) | Additional MZF applications (optional) | 
# Program each chip outside the board (remove from socket, program, re-insert):
minipro -p SST39SF040 -w MROM_ROMDISK_256.bin    # Monitor ROM chip (U1)
minipro -p SST39SF040 -w USER_ROM_256.bin         # User ROM chip 1 (U4)
minipro -p SST39SF040 -w USER_ROM_II_256.bin      # User ROM chip 2 (U5, if fitted)
minipro -p SST39SF040 -w USER_ROM_III_256.bin     # User ROM chip 3 (U6, if fitted)
The Monitor ROM chip (U1) cannot be written in-circuit — the Sharp MZ-80A hardware blocks write access to the Monitor ROM address space. All Flash chips must be programmed before insertion.
-------------------------------------------------------------------------------------------------------- ### Writing the SD Card Image
The pre-built SD card image combines 10 RFS drives (0–9) and 7 CP/M disk images into a single raw binary. It is written directly to the SD card with no partition table. 
# Linux / macOS — replace /dev/sdX with your SD card device (check with lsblk or diskutil):
dd if=SHARP_MZ80A_RFS_CPM_IMAGE_1.img of=/dev/sdX bs=4M status=progress
sync
Any FAT-formatted micro SD card of 2 GB or larger is suitable. The image occupies approximately 500 MB (10 RFS drives + 7 CP/M disk images). Any remaining space on the card beyond the image is unused.
-------------------------------------------------------------------------------------------------------- ### Rom Disk Software
In order to use the Rom Disk Hardware, a comprehensive set of Z80 assembler methods needed to be written to allow bank paging and with it came the ability to upgrade the machines monitor (BIOS) functionality. This Z80 software forms the Rom Filing System which can be found in the Gitea repository under RFS Repository.
Rom Filing System
The Rom Filing System (RFS) is a software upgrade for the Sharp MZ-80A primarily intended for use with the MZ-80A Rom Disk but has now been ported to the tranZPUterFusionX platform as well. The software replaces the Monitor and User ROMs on the motherboard via the Rom Disk daughter card with lifter sockets where up to 4×512 Kbyte Flash RAMs and 1×512 Kbyte Static RAM are sited.
One of the Flash RAMs is paged into the Monitor ROM socket and the other Flash RAM/Static RAM into the User ROM socket. The first 32 Kbytes (8 slots × 4K) of the Monitor Flash RAM and the first 24 Kbytes (12 slots × 2K) of the User Flash RAM is dedicated to paged ROMs, with the remainder used to store Sharp MZF format binary images packed within 256-byte sectors.
On boot the Monitor ROM detects the RFS firmware at address 0xE800 and executes it. RFS initialises and appends + RFS vx.xx to the SA-1510 sign-on banner — this appears regardless of SD card status. The SD card is then initialised separately; if not found or unable to initialise, an error code is printed to indicate the failure. The original * prompt is shown and all original SA-1510 commands remain available alongside the full RFS command set. Please refer to the RFS User Manual, Technical Guide and Developer's Guide for full details.
-------------------------------------------------------------------------------------------------------- ### Sharp MZ-700 Mode
The tranZPUter SW Version 2.1 board has now been developed and RFS software updated to coexist with this board without a K64F processor (the processor can be present but no use of its services will be made under RFS). This board adds Sharp MZ-700 hardware level compatibility logic, both memory management and keyboard remapping are made within hardware.

In order to cater for this upgrade, RFS has been updated to include the MZ-700 1Z-013A monitor ROM and a command to enable it. When enabled, the machine is set to compatibility mode, the 1Z-013A ROM loaded as the primary monitor and reset. The keyboard is remapped real time and so is the memory. Loading S-BASIC, read/write cassette etc works as expected on an MZ-700 whilst phyically running in an MZ-80A.
-------------------------------------------------------------------------------------------------------- ## Obtaining a Rom Disk An MZ-80A Rom Disk can be sourced on Tindie fully built or as a kit of parts (with the Flash ROMS pre-programmed). Alternatively, use the bill of materials below to purchase the parts from your local suppliers/Ebay. ## Required Skill Level Assembly of the PCB requires good SMD soldering skills and a proven technique is as follows: - Using a nano-solder paste in a syringe, inject a little solder onto each pad. - Place components onto the pads, smudging or bridges are not so critical (so long as you don't place excessive solder onto the pad) as the solder consolidates around the source of heat so bridges don't tend to be an issue. - Using a 0.5mm solder bit at approx 350'c, touch each IC and component pin. If a bridge does form, use a needle, whilst applying heat, to draw out the bridge. - Alternatively, use a heat gun at 350'c with fine nozzle and low fan speed, heat up a small section of components until the solder flows and bonds. - On completion, wash the assembled board in Isopropyl Alcohol to remove any surplus nano-solder or flux. Variations on the above can be made using an IR oven (or even a kitchen oven if it reaches 350'c), placing the board complete with solder and components into the oven, watching and waiting until the solder melts then remove and cool. You may need to make some slight corrections to any part which has bridged or not bonded well. ## Bill Of Materials The cost to make a Rom Disk v2.1 can be seen in the table below. This excludes consumables such as solder paste and flux. Please scroll right to see the full table details. Source: MZ80-ROMPG\_v2\_1.sch
Component Count: 68
| Ref | Qty | Price (Unit) | Price (10) | Price (100) | Price Ea (5 Off Sum) | Price Ea (10 Off) | Value | Cmp name | Footprint | Description | Vendor | | | | ----------------------------------------------------------------------------------------------- | -------------------------------------------------- | ------------ | ---------- | ----------- | ----------------- | -------------- | -------------- | -------------------------- | ----------------------------------------------------------------- | | C2, C1, C3, C4, C6, C5, C12, C8, C9, C7, C15, C18, C10, C22, C20, C19, C11, C21, C13, C14, C16, | 21 | 0.2232 | 0.2232 | 0.1117 | 4.6872 | 2.3457 | 100nF | C\_Small | Capacitor\_SMD:C\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Unpolarized capacitor, small symbol | https://uk.farnell.com/multicomp/mc0805f104m500ct/cap-0-1-f-50v-20-y5v-0805/dp/2627484 | | C17, | 1 | 0.0641 | 0.0641 | | 0.0641 | 0.0641 | 100pF | C\_Small | Capacitor\_SMD:C\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Unpolarized capacitor, small symbol | https://uk.farnell.com/vishay/tmcma0j107mtrf/cap-100-f-6-3v-20/dp/2491474 | | C23, | 1 | 0.7116 | 0.7116 | | 0.7116 | 0.7116 | 100uF | CP\_Small | Capacitor\_SMD:C\_1206\_3216Metric\_Pad1.42x1.75mm\_HandSolder | Polarized capacitor, small symbol | https://uk.farnell.com/kemet/c0805c101j1gactu/cap-100pf-100v-5-c0g-np0-0805/dp/1414655 | | D2, D1, | 2 | 0.358 | 0.213 | | 0.716 | 0.426 | 1N5817 | 1N5817 | Diode\_SMD:D\_SOD-123 | 20V 1A Schottky Barrier Rectifier Diode, DO-41 | https://www.mouser.co.uk/ProductDetail/821-B0520LWRHG | | J1, | 1 | 0.582 | 0.582 | | 0.582 | 0.582 | SD CARD | Conn\_01x06 | Connector\_PinSocket\_2.54mm:PinSocket\_1x06\_P2.54mm\_Horizontal | Generic connector, single row, 01x06, script generated (kicad-library-utils/schlib/autogen/connector/) | https://uk.farnell.com/wurth-elektronik/613006143121/connector-rcpt-6pos-1row-2-54mm/dp/2827951 | | JP1, | 1 | 0.2652 | 0.22 | | 0.2652 | 0.22 | A15/A14 | Jumper\_NC\_Dual | Connector\_PinHeader\_2.00mm:PinHeader\_1x03\_P2.00mm\_Vertical | Dual jumper, normally closed | https://uk.farnell.com/te-connectivity/2355045-3/connector-header-3pos-1row-2mm/dp/3289742 | | JP2, | 1 | 0.2652 | 0.22 | | 0.2652 | 0.22 | A15/~WE~ | Jumper\_NC\_Dual | Connector\_PinHeader\_2.00mm:PinHeader\_1x03\_P2.00mm\_Vertical | Dual jumper, normally closed | https://uk.farnell.com/te-connectivity/2355045-3/connector-header-3pos-1row-2mm/dp/3289742 | | JP3, | 1 | 0.2652 | 0.22 | | 0.2652 | 0.22 | A14/~WE~ | Jumper\_NC\_Dual | Connector\_PinHeader\_2.00mm:PinHeader\_1x03\_P2.00mm\_Vertical | Dual jumper, normally closed | https://uk.farnell.com/te-connectivity/2355045-3/connector-header-3pos-1row-2mm/dp/3289742 | | Jumper, JP1-3 | 3 | 0.057 | 0.057 | | 0.171 | 0.171 | | | 2 pin jumper | | https://uk.farnell.com/multicomp/mc-2205bg/mini-shunt-jumper-2way-2mm-pbt/dp/2834677 | | JP4, | 1 | 0 | 0 | | 0 | 0 | ~LTCHRST~ | SolderJumper\_2\_Open | Jumper:SolderJumper-2\_P1.3mm\_Bridged\_Pad1.0x1.5mm | Solder Jumper, 2-pole, open | | | | | JP6, | 1 | 0 | 0 | | 0 | 0 | MOSI SEL | SolderJumper\_3\_Bridged12 | Jumper:SolderJumper-3\_P1.3mm\_Bridged2Bar12\_Pad1.0x1.5mm | 3-pole Solder Jumper, pins 1+2 closed/bridged | | | | | JP7, | 1 | 0 | 0 | | 0 | 0 | UD1 | SolderJumper\_2\_Bridged | Jumper:SolderJumper-2\_P1.3mm\_Bridged\_Pad1.0x1.5mm | Solder Jumper, 2-pole, closed/bridged | | | | | JP8, | 1 | 0 | 0 | | 0 | 0 | UD2 | SolderJumper\_2\_Bridged | Jumper:SolderJumper-2\_P1.3mm\_Bridged\_Pad1.0x1.5mm | Solder Jumper, 2-pole, closed/bridged | | | | | JP9, | 1 | 0 | 0 | | 0 | 0 | UD3 | SolderJumper\_2\_Bridged | Jumper:SolderJumper-2\_P1.3mm\_Bridged\_Pad1.0x1.5mm | Solder Jumper, 2-pole, closed/bridged | | | | | LG1, | 1 | 0 | 0 | | 0 | 0 | Argo Logo | MountingHole | Graphic:Argo | Mounting Hole without connection | | | | | R3, R2, R1, | 3 | 0.122 | 0.045 | | 0.366 | 0.135 | 560R | R\_Small\_US | Resistor\_SMD:R\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Resistor, small US symbol | https://www.mouser.co.uk/ProductDetail/71-CRCW0805560RFKEAC | | R4, | 1 | 0.0106 | 0.0106 | | 0.0106 | 0.0106 | 220R | R\_Small\_US | Resistor\_SMD:R\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Resistor, small US symbol | https://uk.farnell.com/walsin/wr08x2200ftl/res-220r-1-150v-0805-thick-film/dp/2502698 | | R5, R10, | 2 | 0.077 | 0.017 | | 0.154 | 0.034 | 1K8 | R\_Small\_US | Resistor\_SMD:R\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Resistor, small US symbol | https://www.mouser.co.uk/ProductDetail/652-CR0805JW-182ELF | | R8, R7, R6, | 3 | 0.077 | 0.018 | | 0.231 | 0.054 | 1K2 | R\_Small\_US | Resistor\_SMD:R\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Resistor, small US symbol | https://www.mouser.co.uk/ProductDetail/652-CR0805FX-1151ELF | | R9, | 1 | 0.077 | 0.045 | | 0.077 | 0.045 | 10K | R\_Small\_US | Resistor\_SMD:R\_0805\_2012Metric\_Pad1.15x1.40mm\_HandSolder | Resistor, small US symbol | https://www.mouser.co.uk/ProductDetail/71-CRCW080510K0FKEAC | | U2, | 2 | 2.22 | 1.87 | | 4.44 | 3.74 | (Monitor ROM) | 2732\_Socket | Package\_DIP:DIP-24\_W15.24mm\_Socket | REPROM 4 Ko | https://uk.rs-online.com/web/p/pcb-sockets/1981590/?relevancy-data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searchHistory=%7B%22enabled%22%3Atrue%7D | | U3, | 2 | 2.22 | 1.87 | | 4.44 | 3.74 | (User ROM) | 2716\_Socket | Package\_DIP:DIP-24\_W15.24mm\_Socket | REPROM 2KO | https://uk.rs-online.com/web/p/pcb-sockets/1981590/?relevancy-data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searchHistory=%7B%22enabled%22%3Atrue%7D | | U2/U3 Straight Pin Header | 4 | 1.504 | 1.504 | | 6.016 | 6.016 | | | | | https://uk.rs-online.com/web/p/pcb-headers/6742309/?relevancy-data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searchHistory=%7B%22enabled%22%3Atrue%7D | | U1,U4,U5,U6 32pin Turned Pin Socket | 4 | 0.774 | 0.774 | | 3.096 | 3.096 | | | | | https://uk.rs-online.com/web/p/dil-sockets/1974081/?relevancy-data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searchHistory=%7B%22enabled%22%3Atrue%7D | | U5, U4, U1, | 2 | 1.4 | 1.34 | | 2.8 | 2.68 | SST39SF040 | SST39SF040-Memory\_Flash | Package\_DIP:DIP-32\_W15.24mm\_Socket | | https://www.mouser.co.uk/ProductDetail/804-39SF0407CPHE | | U6, | 1 | 4.04 | 3.52 | | 4.04 | 3.52 | AS6C4008-55PCN | AS6C4008-55PCN-Memory\_RAM | Package\_DIP:DIP-32\_W15.24mm\_Socket | | https://uk.rs-online.com/web/p/sram/7444561/?cm_mmc=UK-PPC-DS3A-_-google-_-DSA_UK_EN_Semiconductors_Index-_-SRAM%7C+Products-_-DYNAMIC+SEARCH+ADS&matchtype=b&aud-826607888587:dsa-1212641595354&s_kwcid=AL!7457!3!504893415565!b!!g!!&gclid=Cj0KCQjw4cOEBhDMARIsAA3XDRh4TCTF_wYFuxNMcgRPi_SnsWjU6rH-V_O0fBiKy5KjJ19J3uHoBHIaAuSTEALw_wcB&gclsrc=aw.ds | | | | U7, | 1 | 0.374 | 0.286 | | 0.374 | 0.286 | 74HCT30 | 74LS30 | Package\_SO:SOIC-14\_3.9x8.7mm\_P1.27mm | 8-input NAND | https://www.mouser.co.uk/ProductDetail/771-HCT30D653 | | U8, U16, | 2 | 0.343 | 0.257 | | 0.686 | 0.514 | 74HCT32 | 74LS32 | Package\_SO:SOIC-14\_3.9x8.7mm\_P1.27mm | Quad 2-input OR | https://www.mouser.co.uk/ProductDetail/771-74HCT32D-T | | U9, | 1 | 0.58 | 0.479 | | 0.58 | 0.479 | 74LS04 | 74LS04 | Package\_SO:SOIC-14\_3.9x8.7mm\_P1.27mm | Hex Inverter | https://www.mouser.co.uk/ProductDetail/595-SN74LS04DR | | U10, | 1 | 0.328 | 0.274 | | 0.328 | 0.274 | 74HCT139 | 74LS139 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | Dual Decoder 1 of 4, Active low outputs | https://www.mouser.co.uk/ProductDetail/771-74HCT139D-Q100J | | U11, | 1 | 0.252 | 0.207 | | 0.252 | 0.207 | 74HCT125 | 74LS125 | Package\_SO:SOIC-14\_3.9x8.7mm\_P1.27mm | Quad buffer 3-State outputs | https://www.mouser.co.uk/ProductDetail/771-74HCT125D-T | | U12, U14, U13, | 3 | 0.374 | 0.319 | | 1.122 | 0.957 | 74HCT273 | 74HCT273 | Package\_SO:SOIC-20W\_7.5x12.8mm\_P1.27mm | 8-bit D Flip-Flop, reset | https://www.mouser.co.uk/ProductDetail/771-74HCT273D-T | | U15, U18, | 2 | 0.343 | 0.257 | | 0.686 | 0.514 | 74HCT00 | 74LS00 | Package\_SO:SOIC-14\_3.9x8.7mm\_P1.27mm | quad 2-input NAND gate | https://www.mouser.co.uk/ProductDetail/771-74HCT00D-T | | U17, | 1 | 0.282 | 0.232 | | 0.282 | 0.232 | 74HCT138 | 74LS138 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | Decoder 3 to 8 active low outputs | https://www.mouser.co.uk/ProductDetail/Nexperia/74HCT138D653?qs=P62ublwmbi8MKahyK7iY6g%3D%3D | | U19, | 1 | 0.694 | 0.572 | | 0.694 | 0.572 | 74HCT191 | 74LS191 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | 4-bit Synchronous Up/Down binary Counter | https://www.mouser.co.uk/ProductDetail/595-CD74HCT191M | | U20, | 1 | 0.343 | 0.281 | | 0.343 | 0.281 | 74HCT595 | 74LS595 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | 8-bit serial in/out Shift Register 3-State Outputs | https://www.mouser.co.uk/ProductDetail/771-74HCT595DQ100118 | | U21, | 1 | 0.411 | 0.361 | | 0.411 | 0.361 | 74HCT163 | 74LS163 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | Synchronous 4-bit programmable binary Counter | https://www.mouser.co.uk/ProductDetail/771-HCT163D653 | | U22, | 1 | 0.442 | 0.376 | | 0.442 | 0.376 | 74HCT165 | 74LS165 | Package\_SO:SOIC-16\_3.9x9.9mm\_P1.27mm | Shift Register 8-bit, parallel load | https://www.mouser.co.uk/ProductDetail/771-74HCT165D-T | | Y1, | 1 | 0.442 | 0.418 | | 0.442 | 0.418 | 16MHz | Crystal\_Small | Crystal:Crystal\_SMD\_Abracon\_ABM3-2Pin\_5.0x3.2mm | Two pin crystal, small symbol | https://www.mouser.co.uk/ProductDetail/815-ABM3-16-B2-T | | SD Card Adaptor | 1 | 2.77 | 2.6 | | 2.77 | 2.6 | | | | | https://www.ebay.co.uk/itm/233362415633?hash=item36557be011:g:-xwAAOSwXk1dmxM7 | | PCB - PCBWay | 1 | 3.7635 | 3.7635 | | 3.7635 | 3.7635 | | | | | | | | | | | | | | | | | | | | | | | | Sub Total | | | | | 46.5736 | 39.8655 | | | | | | | | | P&P | | | | | 5 | 5 | | | | | | | | | VAT @ 20% | | | | | 10.315 | 8.9731 | | | | | | | | | Total (GBP) | | | | | 61.89 | 53.84 | | | | | | | |
The price for one off is not really representative as some components have to be bought in multiples of 10/50/100, ie. the PCB alone cost USD80 (inc taxes) for 10 and the extra cost of buying multiples amortized over the number of boards built.
## Credits
Where I have used or based any component on a 3rd parties design I have included the original authors copyright notice within the headers or given due credit. All 3rd party software, to my knowledge and research, is open source and freely useable, if there is found to be any component with licensing restrictions, it will be removed from this repository and a suitable link/config provided.
## Licenses
This design, hardware and software, is licensed under the GNU Public Licence v3.
### The Gnu Public License v3
The source and binary files in this project marked as GPL v3 are free software: you can redistribute it and-or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

The source files are distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.