ceharris/single-step-65021Single step controller module for the 6502 microprocessor
Single step-6502 is an open-source printed circuit board by ceharris, from the ceharris/single-step-6502 repository on GitHub. It is a 2-layer board of 87.5 × 60 mm with 33 parts on 29 nets, routed with 151 tracks and 1 via.
It is built around the 74HC00D, 74HC123D and 74HC73D, with the NE555P among its other parts. Its parts include 9 capacitors, 9 resistors, 4 ICs, 4 diodes and 2 switches. It belongs with the retro computing and games boards of this library.
This repository contains KiCad sources for a simple single-step controller module for the 6502 microprocessor. It's designed to be connected to the system under test using jumpers. It has a pin header that provides +5 VDC, ground, and the 6502's SYNC and RDY signal paths.
The controller has two push buttons.
The buttons are debounced via the 555 and 74123 ICs to avoid triggering multiple step pulses.
The circuit is designed with a diode such that it can be connected to the 6502's RDY input without disrupting other uses of the signal.
See single-step-6502.pdf for a full description of the circuit design.
| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 100 nF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C3, C6, C7, C8, C9 |
| 4 | 1K | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R2, R3, R7, R9 |
| 4 | MountingHole_Pad | MountingHole:MountingHole_2.2mm_M2_DIN965_Pad | H1, H2, H3, H4 |
| 2 | 100K | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R4, R8 |
| 2 | 10K | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R1, R5 |
| 1 | 1.5K | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R6 |
| 1 | 10 nF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C4 |
| 1 | 1N914 | Diode_THT:D_A-405_P7.62mm_Horizontal | D3 |
| 1 | 2.2 µF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C5 |
| 1 | 4.7 µF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C1 |
| 1 | 47 pF | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm | C2 |
| 1 | 74HC00 | Package_DIP:DIP-14_W7.62mm_Socket | U3 |
| 1 | 74HC123 | Package_DIP:DIP-16_W7.62mm_Socket | U1 |
| 1 | 74HC73 | Package_DIP:DIP-14_W7.62mm_Socket | U2 |
| 1 | BLUE | LED_THT:LED_D5.0mm | D4 |
| 1 | Conn_01x04_Pin | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Horizontal | J1 |
| 1 | GREEN | LED_THT:LED_D5.0mm | D1 |
| 1 | NE555P | Package_DIP:DIP-8_W7.62mm_Socket | U5 |
| 1 | RED | LED_THT:LED_D5.0mm | D2 |
| 1 | SW_Push | Button_Switch_THT:SW_PUSH-12mm | SW2 |
| 1 | SW_Push | Button_Switch_THT:SW_PUSH_6mm | SW1 |
It measures 87.5 × 60 mm and has 2 copper layers, 1.6 mm thick.
33 parts, built around the 74HC00D, 74HC123D, 74HC73D and NE555P. 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.
From the ceharris/single-step-6502 repository on GitHub, at the commit this page was made from: the board is single-step-6502.kicad_pcb and its schematic single-step-6502.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask ceharris before reusing the design.
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