2 layers158.8 × 91.4 mm
Nabu MEGAMAPPER
tergav17/Z80-MegaMapper
Z80 interposer board providing extended memory and I/O instruction mapping
42 parts1
2 layers104.1 × 102.9 mm
ISA EMS
hightower70/ISA_EMS22MByte 8-bit ISA EMS Memory Card for IBM PC XT compatible computers
- Size
- 104.1 × 102.9 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 32
- Nets
- 89
- Pads
- 348
- Tracks, vias
- 1,239, 185
- Pours
- 6
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 29 Jan 2025
- Updated
- 29 Jan 2025
Overview
ISA EMS is an open-source printed circuit board by hightower70, from the hightower70/ISA_EMS repository on GitHub, published under the Apache-2.0 licence. It is a 2-layer board of 104.1 × 102.9 mm with 32 parts on 89 nets, routed with 1,239 tracks and 185 vias.
It is built around the 74LS245SC, AS6C4008-55PCN and 74LS670, with the 74LS139PC among its other parts. Its parts include 12 capacitors, 10 ICs and 2 connectors.
Main components
474LS245SC
-0℃~+70℃ 12ns@5V,45pF 15mA 24mA 4.75V~5.25V 74LS 8 Bidirectional Output enable Schmitt trigger Tri-State - Buffers, Drivers, Receivers, Transceivers ROHSTexas InstrumentsBuffers, Drivers, Receivers, Transceivers
AS6C4008-55PCN
PDIP-320℃~+70℃ 2.7V~5.5V 30mA 4Mbit 4uA 55ns Parallel Port (Parallel) PDIP-32 SRAM ROHSAlliance MemorySRAM74LS670
-Specialty LogicTexas Instruments
74LS139PC
PDIP-1622ns 74LS 8mA Decoder Single Supply PDIP-16 Signal Switches, Multiplexers, DecodersonsemiSignal Switches, Multiplexers, Decoders
README
README.md2MByte ISA EMS Expansion Card for IBM PC XT computers
This is a redesign of the lo-tech.co.uk 2Mb ISA EMS board with some changes:
- All thru-hole instead of SMD, while retaining a rather compact format
- Simplified address decoding and storage circuits for less chip count
All design files and gerber files for PCB manufacturing are avaiable in the repository. The schematics schematics is also avaiable in PDF format.
The card was tested in modern replica of an XT computer like Xi8088 and Micro8088 without issues.
Configuration
To configure the EMS, jumpers on J2 header are used.
Pins pairs 1 and 2 configure the Page Frame base address, while 3 and 4 configure the IO Port base address.
Page Frame Address:
| 1 | 2 | EMS Page Frame Base |
|---|---|---|
| X | X | C000h |
| - | X | D000h |
| X | - | E000h |
| - | - | Invalid |
Port Base Address
| 3 | 4 | EMS IO Port Base |
|---|---|---|
| X | X | 260-263h |
| - | X | 264-267h |
| X | - | 268-26Bh |
| - | - | 26C-26Fh |
(-=no jumper (opened), X=jumper (closed))
Usage
You need a memory manager to use this board. I'm including the LTEMM driver provided by lo-tech in this repository. Please refer to this page regarding the terms of use.
Bill of Materials
All ICs are in DIP package.
- C1,C4 ,C5 ,C6, C7, C8, C9, C10, C11, C12: 100nF, ceramic
- C2, C3: 10uF / 50v electrolytic caps
- J2 2x4 2.5mm breakable header
- RN1: resistor network, 10k, bussed, 5 pins
- RN2: resistor network, 10k, bussed, 9 pins.
- U1, U2, U3, U4: AS6C4008-55PCN (You don't need to fill all sockets: fit as much memory as you need starting from socket 1!)
- U5: 74LS139
- U6: 74LS245
- U7, U10: 74HCT688
- U8, U9: 74LS670
- ISA bracket: Keystone 9202, plus screws.
Credits
- Thanks to hkzab for publishing a similar design
- Thanks to lo-tech.co.uk for having published their schematics
- Thanks to Sergey for all his projects!
Parts
32| Qty | Value | Footprint | References |
|---|---|---|---|
| 10 | 100nF | Capacitor_THT:C_Disc_D6.0mm_W2.5mm_P5.00mm | C1, C4, C5, C6, C7, C8, C9, C10, C11, C12 |
| 4 | AS6C4008-55PCN | Package_DIP:DIP-32_W15.24mm | U1, U2, U3, U4 |
| 2 | 10uF | Capacitor_THT:CP_Radial_D5.0mm_P2.50mm | C2, C3 |
| 2 | 74LS670 | Package_DIP:DIP-16_W7.62mm | U8, U9 |
| 2 | 74LS688 | Package_DIP:DIP-20_W7.62mm | U7, U10 |
| 1 | 10k | Resistor_THT:R_Array_SIP9 | RN1 |
| 1 | 10k | Resistor_THT:R_Array_SIP5 | RN2 |
| 1 | 74LS139 | Package_DIP:DIP-16_W7.62mm | U5 |
| 1 | 74LS245 | Package_DIP:DIP-20_W7.62mm | U6 |
| 1 | EMS Address | Connector_PinHeader_2.54mm:PinHeader_2x04_P2.54mm_Vertical | J2 |
| 1 | ISA BUS | ISA_EMS:BUS_XT | J1 |
| 1 | MountingHole_Pad | MountingHole:MountingHole_3mm_Pad | H1 |
| 1 | MountingHole_Pad | MountingHole:MountingHole_3.5mm_Pad_TopBottom | H2 |
The 28 most common of 32 parts.
Questions
How big is the ISA EMS PCB?
It measures 104.1 × 102.9 mm and has 2 copper layers, 1.6 mm thick.
What parts does the ISA EMS use?
32 parts, built around the 74LS245SC, AS6C4008-55PCN, 74LS670 and 74LS139PC. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the ISA EMS KiCad files?
From the hightower70/ISA_EMS repository on GitHub, at the commit this page was made from: the board is ISA_EMS.kicad_pcb and its schematic ISA_EMS.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the ISA EMS design in my own project?
Its repository publishes it under the Apache-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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