Note that this is not a fully tested project at this point. . . .
This is based Rob Krenicki's design that is based on the HackMac KiCAD schematics. I have made several changes to the original design including:
- Placing 32K of 16bit wide fast ram on the board to fully populate the address space
- Placing an EPROM on the main board that can be used as an on-board cartridge ROM
- adding a header to allow a microcontroller to replace the GROM chips (hopefully this can be moved on-board soon)
- replacing the video DRAM with SRAM
- Updating the Keyboard header to support a soft caps lock switch on the keyboard PCB
- designing a Cherry MX keyboard
- adding headers for the GROM and expansion port to support riser cards for these ports
If there are any questions, I can be reached at vic2020Dan at gmail dot com.
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Cleanup/Documentation Possible Future Thoughts:
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Redo the Board in an ATX form factor with PEB slots on board
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Add Support for the Pico9918 on-board
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Add Support for a Tang Nano FPGA TMS9918 replacement
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Add Hex-bus port
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Add a DIN 5-pin Composite video/Audio out.
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Add built in speech synthesis
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Clone Disk IO card
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Relocate all the ports to the back of the motherboard
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It has been suggested that we also have a console style version of the next revision as not everyone has a desire for a larger PE style machine
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Also perhaps add some keys to the keyboard
The DIP switch on the main board allows one to configure which bank areas are populated with RAM.
RAM0 enables RAM to addresses >2000-3FFF (Lo Memory Expansion) RAM1 enables RAM to addresses >A000-BFFF (Hi Memory Expansion) RAM2 enables RAM to addresses >C000-DFFF (Hi Memory Expansion) RAM3 enables RAM to addresses >E000-FFFF (Hi Memory Expansion) RAM4 enables RAM to addresses >8000-83FF (Normal TI Scratch Pad RAM)
Note that I have never actually tested off-board 8 bit RAM, so this is new territory and might need some debugging 😊
also on-board RAM is 16 bit – so all of those external RAM sources will be slower.
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on rev 0.95 R36-40 are listed as 100K ohm, they are actually 100 ohm
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on rev 0.95 the joystick and cassette connectors are mirrored and need to be mounted on the bottom side of the board to function
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Both of these are corrected in 0.96
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The reset button J1 should be attached to pin 5 of U1 not Pin 4
| Qty | Reference(s) | Part |
|---|---|---|
| 6 | C1, C9, C11, C58, C73, C75 | 0.001uF |
| 1 | C2 | 22pF |
| 3 | C3, C5, C59 | 22uF |
| 12 | C4, C7, C13, C14, C20, C54, C55, C62, C64, C68, C71, C74 | 0.1uF |
| 1 | C6 | 1uF |
| 7 | C8, C52, C63, C65, C66, C67, C72 | 0.01uF |
| 1 | C10 | 100uF |
| 1 | C12 | 0.01uF |
| 7 | C15, C16, C17, C19, C21, C22, C60 | 100uF |
| 30 | C18, C23, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33, C34, C35, C36, C37, C38, C39, C40, C41, C42, C43, C44, C45, C46, C47, C48, C49, C50, C51 | 0.1uF |
| 1 | C53 | 100uF |
| 1 | C56 | 12pF |
| 1 | C57 | 56pF |
| 1 | C61 | 220uF |
| 1 | C69 | 220pF |
| 1 | C70 | 0.022uF |
| 2 | CR1, CR4 | 1N4148 |
| 2 | CR2, CR3 | 1N914B |
| 1 | D1 | LED |
| 1 | J1 | Connector PinHeader 2.54mm:PinHeader 1x02 P2.54mm Vertical |
| 1 | J2 | Connector PinHeader 2.54mm:PinHeader 1x02 P2.54mm Vertical |
| 1 | J3 | TerminalBlock RND:TerminalBlock RND 205-00278 1x04 P5.00mm Vertical |
| 1 | J4 | Connector PinHeader 2.54mm:PinHeader 1x16 P2.54mm Vertical |
| 2 | J5, J6 | Connector PinHeader 2.54mm:PinHeader 1x03 P2.54mm Vertical |
| 1 | J7 | Connector PinHeader 2.54mm:PinHeader 1x03 P2.54mm Vertical |
| 1 | J8 | Connector PinHeader 2.54mm:PinHeader 1x02 P2.54mm Vertical |
| 1 | J9 | Connector PinHeader 2.54mm:PinHeader 1x02 P2.54mm Vertical |
| 1 | J10 | Connector Dsub:DSUB-9 Female Horizontal P2.77x2.84mm EdgePinOffset4.94mm Housed MountingHolesOffset7.48mm |
| 1 | J11 | Connector PinHeader 2.54mm:PinHeader 1x18 P2.54mm Vertical |
| 1 | J12 | Connector PinHeader 2.54mm:PinHeader 2x22 P2.54mm Vertical |
| 1 | J13 | WernerCustomLibrary:44 Pin Card Edge |
| 1 | J14 | Library:CardEdge 34Pin 2.54mm Vertical |
| 1 | J15 | Connector PinHeader 2.54mm:PinHeader 2x18 P2.54mm Vertical |
| 1 | J16 | Connector PinSocket 2.54mm:PinSocket 1x03 P2.54mm Vertical |
| 1 | J17 | Connector PinSocket 2.54mm:PinSocket 1x03 P2.54mm Vertical |
| 1 | J18 | Connector Dsub:DSUB-9 Female Horizontal P2.77x2.84mm EdgePinOffset4.94mm Housed MountingHolesOffset7.48mm |
| 1 | L1 | 0.33uH |
| 2 | L4, L5 | 6.8uH |
| 1 | L7 | 5.8uH |
| 1 | L8 | INDUCTOR (Ferrite BEAD) |
| 7 | L10, L11, L12, L13, L14, L15, L16 | 8.2uH |
| 3 | Q1, Q3, Q4 | TIS92 |
| 1 | Q2 | 2N3904 |
| 1 | R1 | 150k |
| 7 | R2, R9, R11, R18, R34, R35, R46 | 1k |
| 1 | R3 | 12k |
| 1 | R4 | 47k |
| 4 | R5, R6, R7, R8 | 22 |
| 5 | R10, R26, R45, R52, R53 | 4.7k |
| 5 | R12, R13, R14, R15, R16 | 1K |
| 3 | R17, R48, R50 | 2.2k |
| 2 | R19, R30 | 470 |
| 1 | R20 | 270 |
| 1 | R21 | 1.5k x 9 SIP bussed |
| 1 | R22 | 361 |
| 3 | R23, R73, R75 | 5.6k |
| 2 | R24, R27 | 10 |
| 1 | R25 | 150 |
| 1 | R28 | 470k |
| 1 | R29 | 0 |
| 2 | R31, R33 | 75 |
| 1 | R32 | 470 |
| 4 | R41, R42, R43, R44 | 62 |
| 1 | R47 | 3.3k |
| 9 | R36, R37, R38, R39, R40, R49, R51, R54, R56 | 100 |
| 1 | R55 | 330 |
| 1 | R57 | 10k |
| 1 | R58 | 6.8k |
| 1 | R59 | 39k |
| 1 | R60 | 6.8k |
| 4 | R61, R62, R67, R68 | 1K |
| 1 | R63 | 120k |
| 1 | R64 | 2.7k |
| 3 | R65, R66, R76 | 220 |
| 1 | R69 | 10K |
| 1 | R70 | 9.1k |
| 2 | R71, R72 | 10k |
| 1 | R74 | 5.6K |
| 1 | R77 | 15 |
| 2 | RN1, RN2 | 10K x 9 SIP Bussed |
| 1 | SW1 | DIP switchx05 |
| 1 | SW2 | Pin Header 01x02 Male |
| 1 | U1 | TMS9904 (note this needs to be a 9904 not 9904ANL. If the 9904ANL is used, Y1 needs to be substituted with 12Mhz, L1 needs to be substituted with 3.3uh and C2 needs to be substituted with 50pf) |
| 1 | U2 | TMS9900 |
| 4 | U3, U15, U22, U24 | 74LS04 |
| 2 | U4, U9 | 74LS32 |
| 2 | U5, U8 | 74LS138 |
| 1 | U6 | 74LS03 |
| 1 | U7 | 74LS08 |
| 3 | U10, U14, U18 | 74LS00 |
| 2 | U11, U41 | 74LS244 |
| 1 | U12 | 74LS373 |
| 1 | U13 | 74LS245 |
| 1 | U16 | 74LS74 |
| 1 | U17 | 74LS194 |
| 1 | U19 | LM2901 |
| 1 | U20 | LM7905 TO220 |
| 1 | U21 | LM2903 |
| 3 | U26, U27, U28 | TMC0430 |
| 3 | U29, U30, U37 | HM62256BLP |
| 2 | U31, U32 | 27C64 |
| 1 | U33 | SN76489 |
| 1 | U34 | TMS9918 |
| 3 | U35, U36, U38 | 74LS574 |
| 1 | U39 | TMS9901 |
| 1 | U40 | 74LS156 |
| 2 | U42, U43 | 74LS367 |
| 1 | U44 | 74LS379 |
| 1 | U45 | 27C010 |
| 1 | U46 | RC4558 |
| 1 | U47 | 74LS06 |
| 2 | U48, U49 | TIL119 |
| 1 | Y1 | 48.000 MHz Crystal |
| 1 | Y2 | 10.7MHz Crystal |
| Qty | Reference(s) | Value | Part |
|---|---|---|---|
| 1 | C1 | 0.1uF | Capacitor |
| 1 | D1 | LED | LED |
| 1 | D2 | LED | LED |
| 1 | J1 | Pin Header 1x18 male | Pin Header 1x18 male |
| 2 | R1, R2 | 470 ohm | Resistor |
| 1 | R3 | 1K ohm | Resistor |
| 48 | SW1-SW48 | Mechanical Switch | Cherry MX Switch (or compatible) |
| 1 | U1 | ATtiny13A-P | IC |
| 1 | U2 | 74LS125 | IC |
| 3 | Switch Stabilizer 2.25 | ||
| 1 | Switch Stabilizer 6.25 | ||
| 1 | Optional Alignment frame (will need modified) | ||
| Stabilizers (frame not used): | https://www.amazon.com/Genuine-Cherry-PCB-Snap-Stabilizers/dp/B085T8QZJC | ||
| Stabilizers (Frame used) | https://www.amazon.com/dp/B082X4V9VC | ||
| Frame: | https://www.amazon.com/gp/product/B07MMB33WG |
| Qty | Reference(s) | Part | Type |
|---|---|---|---|
| 1 | J1 | Pin Header 01x18 Male | Pin Header 01x18 Male |
| 1 | J2 | 36 Pin Edge Connector | CONN EDGE DUAL FMALE 36POS 0.100 spacing |
| Qty | Reference(s) | Part | Type |
|---|---|---|---|
| 1 | J1 | Pin Header 2x22 Male | Pin Header 2x22 Male |
| Qty | Reference(s) | Part | Type |
|---|---|---|---|
| 1 | J1 | Pin Header Socket 01x16 Female Right Angle | Pin Header Socket 01x16 Female Right Angle |
| 4 | U1-U4 | Level Shifter | https://www.amazon.com/KeeYees-Channels-Converter-Bi-Directional-Shifter/dp/B07LG646VS |
| 1 | U5 | ESP32 Devkit | https://www.amazon.com/Development-Microcontroller-Integrated-Antenna-Amplifiers/dp/B09GK74F7N |
The original project was licensed under the Creative Commons - Attribution - ShareAlike 3.0 License
This board was derrived from works by, uses design elements from, or contains sofware writen by the following:
- Rob Krenicki (https://github.com/rkrenicki/TI99-Motherboard)
- HackMac (https://bitbucket.org/hackmac/ti-schematics/wiki/Home)