JTAG Pinout

Looking for JTAG Cable? Learn about various JTAG pinouts.

Unfortunately there is no standard JTAG pinout. Usually the JTAG connector is a simple two row header on a center-line with 0.1 inches pin-to-pin spacing. This page lists pinouts for common JTAG connectors. You can use this information to help you create custom JTAG cable or to connect your JTAG hardware to existing JTAG interface.

There are many JTAG header arrangements, from 10-pin to 20-pin headers. If you are designing with ARM or MIPS microprocessor, we recommend using appropriate JTAG connector (EJTAG or ARM JTAG) to maintain compatibility with development tools. In other cases we recommend you using JTAG connector for manufacturer of your part or AVR/Byteblaster JTAG (which is compatible with many other products) or standard 8 pin "PLD" JTAG connector.

Daisy chaining multiple devices

If your design uses multiple devices with JTAG TAP, you must either use separate connector for each device or chain devices. Generally, JTAG supports many devices in single JTAG chain, but many tools are not compatible with this feature. Check tool's documentation before you put devices into chain.

8 Pin PLD-JTAG JTAG pinout


1	VCC
2	TDO
3	TDI
4	nSRST
5
6	TMS
7	GND
8	TCK

10 Pin AVR JTAG pinout


1	TCK	GND	2
3	TDO	VREF	4
5	TMS	nSRST	6
7	-	nTRST	8
9	TDI	GND	10

10 Pin Altera ByteBlaster JTAG pinout


1	TCK	GND	2
3	TDO	VREF	4
5	TMS	-	6
7	-	-	8
9	TDI	GND	10

10 Pin Maxim MAXQ JTAG header pinout


1	TCK	GND	2
3	TDO	VREF	4
5	TMS	nSRST	6
7	-	VSUPPLY	8
9	TDI	GND	10

10 Pin Actel FlashPro JTAG pinout


1	TCK	GND	2
3	TDO	-	4
5	TMS	VJTAG	6
7	VPUMP	TRST	8
9	TDI	GND	10

10 Pin Cypress Ultra ISR JTAG pinout


1	GND	TMS	2
3	JTAGEN	TCK	4
5	ISR	TDI	6
7	VREF		8
9	TDO	GND	10

10 Pin Lattice JTAG pinout


1	TCK	-	2
3	TMS	GND	4
5	TDI	VREF	6
7	TDO	GND	8
9	nTRST	nISPEN	10

9 Pin Lattice ispDOWNLOAD USB cable JTAG Header pinout


1	VCC
2	TDO
3	TDI
4	ispEN#
5	nTRST
6	TMS
7	GND
8	TCK
9	-

12 Pin JTAG pinout

Found in Linksys routers such as the WRT54G and WRT54GS, the 12-pin header has the following arrangement of JTAG signals and pins:


1	nTRST	GND	2
3	TDI	GND	4
5	TDO	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	nSRST	GND	12

Seems, this header is a truncated version of the full EJTAG header.

14 Pin JTAG Header

This header is fully MIPS EJTAG 2.6 compatible and described in the EJTAG 2.6 standard. Found in Edimax routers (and other mostly embedded devices, including on many WiFi devices), the 14-pin header has the following arrangement of JTAG signals and pins:


1	nTRST	GND	2
3	TDI	GND	4
5	TDO	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	nSRST	n/a	12
13	n/a	Vcc	14

A buffered JTAG cable such as the Wiggler requires an external Vcc voltage supply. The 14-pin header conveniently supplies this voltage on pin 14. The typical unbuffered JTAG cable, however, does not require an external voltage in order to function. Formally, the pin 14 is called VREF and used to indicate a JTAG signal levels: 5V, 3.3V or 2.5V. On the most devices this pin is tied to the device's Vcc and may be used to power a buffer IC chip (and to generate an appropriate levels as result). Note that the 12-pin JTAG header arrangement does not provide Vcc.

14 Pin ARM JTAG Header


1	VREF	GND	2
3	nTRST	GND	4
5	TDI	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	TDO	nSRST	12
13	VREF	GND	14

14 Pin Texas Instruments MSP430 JTAG pinout


1	TDO	VREF	2
3	TDI	-	4
5	TMS	TCLK	6
7	TCK	VPP	8
9	GND	-	10
11	nSRST	-	12
13	-	-	14

9 Pin Xilinx Parallel III and IV JTAG pinout


1	VREF
2	GND
3	-
4	TCLK
5	-
6	TDO
7	TDI
8	-
9	TMS

14 Pin Xilinx Parallel IV JTAG Header pinout


1	VGND	VREF	2
3	GND	TMS	4
5	GND	TCK	6
7	GND	TDO	8
9	GND	TDI	10
11	GND	-	12
13	GND	-	14

20 Pin Toshiba MIPS JTAG header


1	nTRST	-	2
3	TDI	GND	4
5	TDO	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	VREF	GND	12
13	nSRST	-	14
15	-	-	16
17	-	-	18
19	-	-	20

20 Pin Philips MIPS JTAG header pinout


1	nTRST	GND	2
3	TDI	GND	4
5	TDO	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	nSRST	GND	12
13	-	GND	14
15	-	GND	16
17	-	GND	18
19	-	GND	20

20 Pin ARM JTAG Header

Used with almost all ARM-based microcontrollers.


1	VREF	VSUPPLY	2
3	nTRST	GND	4
5	TDI	GND	6
7	TMS	GND	8
9	TCK	GND	10
11	RTCK	GND	12
13	TDO	GND	14
15	nSRST	GND	16
17	DBGRQ	GND	18
19	DGBACK	GND	20

JTAG Cables

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