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## 18 Boundary Scan Commands

One of the original purposes of JTAG was to support boundary scan based hardware testing. Although its primary focus is to support On-Chip Debugging, OpenOCD also includes some boundary scan commands.

### 18.1 SVF: Serial Vector Format

The Serial Vector Format, better known as SVF, is a way to represent JTAG test patterns in text files. In a debug session using JTAG for its transport protocol, OpenOCD supports running such test files.

— Command: svf filename [`quiet`]

> This issues a JTAG reset (Test-Logic-Reset) and then runs the SVF script from `filename`. Unless the `quiet` option is specified, each command is logged before it is executed.

### 18.2 XSVF: Xilinx Serial Vector Format

The Xilinx Serial Vector Format, better known as XSVF, is a binary representation of SVF which is optimized for use with Xilinx devices. In a debug session using JTAG for its transport protocol, OpenOCD supports running such test files.

> Important: Not all XSVF commands are supported.

— Command: xsvf (tapname|`plain`) filename [`virt2`] [`quiet`]

> This issues a JTAG reset (Test-Logic-Reset) and then runs the XSVF script from `filename`. When a tapname is specified, the commands are directed at that TAP. When `virt2` is specified, the xruntest command counts are interpreted as TCK cycles instead of microseconds. Unless the `quiet` option is specified, messages are logged for comments and some retries.

The OpenOCD sources also include two utility scripts for working with XSVF; they are not currently installed after building the software. You may find them useful:

- svf2xsvf ... converts SVF files into the extended XSVF syntax understood by the `xsvf` command; see notes below.
- xsvfdump ... converts XSVF files into a text output format; understands the OpenOCD extensions.

The input format accepts a handful of non-standard extensions. These include three opcodes corresponding to SVF extensions from Lattice Semiconductor (LCOUNT, LDELAY, LDSR), and two opcodes supporting a more accurate translation of SVF (XTRST, XWAITSTATE). If xsvfdump shows a file is using those opcodes, it probably will not be usable with other XSVF tools.