Arm JTAG 20 (IEEE 1149.1 / SWD)
Standard ARM 20-Pin 0.1-inch JTAG & SWD Debug Header Pinout
The 20-pin ARM JTAG header is the classic 0.1-inch debug connector used by JTAG and Serial Wire Debug probes. Select a contact to see its signal and role.
Pin assignment
- Power
- Not connected
- Debug (JTAG/SWD)
- Ground
Schematic face view, not to scale · numbering per Arm JTAG 20 (IEEE 1149.1 / SWD)
| Pin | Signal | Function | Status |
|---|---|---|---|
| VTREF | Target reference voltage: the probe matches its logic levels to it and detects the target when it exceeds 0.8 V | Standard | |
| NC | Not connected in the Arm pinout | Discretionary | |
| nTRST | JTAG Test Reset (active low) | Standard | |
| GND | Ground | Standard | |
| TDI | JTAG Test Data In | Standard | |
| GND | Ground | Standard | |
| TMS / SWDIO | JTAG Test Mode Select / SWD Data I/O | Standard | |
| GND | Ground | Standard | |
| TCK / SWCLK | JTAG Test Clock / SWD Clock | Standard | |
| GND | Ground | Standard | |
| RTCK | Returned Test Clock (adaptive clocking) | Standard | |
| GND | Ground | Standard | |
| TDO / SWO | JTAG Test Data Out / Serial Wire Output | Standard | |
| GND | Ground | Standard | |
| nSRST | System Reset (active low) | Standard | |
| GND | Ground | Standard | |
| DBGRQ | Debug Request (optional) | Discretionary | |
| GND | Ground | Standard | |
| DBGACK | Debug Acknowledge (optional) | Discretionary | |
| GND | Ground | Standard |
Pin details
Select a pin on the diagram or table for full details.
About this connector
Standard 20-pin ARM JTAG and SWD debug connector with target reference voltage, debug signals, reset, and ground returns.
Specifications
- Standard
- ARM 20-Pin 2.54mm Pitch
- Positions
- 20
Primary sources
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