OrigenJTAG (0.19.1)


This plugin provides an ATE driver for an IEEE 1149.1 compliant JTAG interface.

It makes no assumptions about the instruction or data register attributes or higher level protocol concerns. For use at DUT model level this plugin would be normally be wrapped in a higher level protocol such as Nexus.

How To Import

In your Gemfile add:

gem "origen_jtag", ">= 0.19.1"

or if your application is a plugin add this to your .gemspec

spec.add_development_dependency "origen_jtag", ">= 0.19.1"

NOTE: You will also need to include require 'origen_jtag' somewhere in your environment. This can be done in config/environment.rb for example.

How To Use

New Style Example

The driver no longer requires specific pin names (or aliases), supports sub_block instantiation and DUTs with multiple JTAG ports. You are no longer required to include “OrigenJTAG” in your DUT class.

Here is an example integration:

class Pioneer

  include Origen::TopLevel

  def initialize
    add_pin :tclk
    add_pin :tdi
    add_pin :tdo
    add_pin :tms

    add_pin :tck2
    add_pin :tdi2
    add_pin :tdo2
    add_pin :tms2

    # In this first instance TCK covers 4 tester cycles,
    # 2 high then 2 low for each effective TCK pulse.
    # Strobe TDO only when TCK high.  Only store TDO on last cycle (3)

    # several pluggins use dut.jtag, your default port driver should be named jtag for compatibility
    sub_block :jtag, class_name: 'OrigenJTAG::Driver',
                     tclk_format:       :rl,
                     tclk_multiple:     4,
                     tdo_strobe:        :tclk_high,
                     tdo_store_cycle:   3,
                     tck_pin:           pin(:tclk),
                     tdi_pin:           pin(:tdi),
                     tdo_pin:           pin(:tdo),
                     tms_pin:           pin(:tms)

    # create a driver for a 2nd port like this
    # note different configuration settings can be used
    sub_block :jtag_port2, class_name: 'OrigenJTAG::Driver',
                     tclk_format:       :rh,
                     tclk_multiple:     2,
                     tdo_strobe:        :tclk_high,
                     tdo_store_cycle:   1,
                     tck_pin:           pin(:tck2),
                     tdi_pin:           pin(:tdi2),
                     tdo_pin:           pin(:tdo2),
                     tms_pin:           pin(:tms2)


dut.jtag                # => jtag driver for the first port (tclk, tdi, tdo, tms)
dut.jtag_port2          # => jtag driver for the second port (tck2, tdi2, tdo2, tms2)

By default, the driver will apply the conventional ‘1’ and ‘0’ drive values on the TCK pin to turn the clock on and off, however this can be overridden by supplying the :tclk_vals option as shown in the example below:

# My V93K timing setup uses 'P' to enable a clock pulse instead of '1'
tclk_vals: { on: 'P', off: 0 }

Legacy Example

Include the OrigenJTAG module to add a JTAG driver to your class and define the required pins. Normally the pins would be an alias to existing DUT pins and therefore the JTAG driver module cannot assume them.

Including the module adds a jtag method which will return an instance of OrigenJTAG::Driver.

The following attributes can be customized by defining a JTAG_CONFIG hash:

  • tclk_format - TCLK timing format, Return High (:rh) or Return Low (:rl). Default is :rh.
  • tclk_multiple - Number of cycles for a single TCLK pulse to cover, to support cases where TCLK needs to be a fraction of another clock period. Assumes 50% duty cycle, specify only even numbers if > 1. Default is :r1.
  • tdo_strobe - When using multiple cycles for TCK, which state of TCK to strobe for TDO, :tclk_high or :tclk_low or :tclk_all. Default :tclk_high.
  • tdo_store_cycle - When using multiple cycles for TCK, which cycle of TCK to store for TDO if store requested (0 to number of tclk_multiple-1). Default 0

Here is an example integration:

class Pioneer

  include OrigenJTAG
  include Origen::Pins

  # TCK covers 4 tester cycles, 2 high then 2 low for each effective TCK pulse
  # Strobe TDO only when TCK high.  Only store TDO on last cycle (3)
    :tclk_format => :rl,
    :tclk_multiple => 4,
    :tdo_strobe => :tclk_high,
    :tdo_store_cycle => 3,

  def initialize
    add_pin :tclk
    add_pin :tdi
    add_pin :tdo
    add_pin :tms


Pioneer.new.jtag  # => An instance of OrigenJTAG::Driver


Two APIs are provided, the primary one provides canned methods to read and write to the IR and DR registers.

These accept either an absolute data value or an Origen register/bit collection.

jtag.write_dr 0x1234, :size => 16

# The size option is not required when a register is supplied
jtag.write_dr $dut.reg(:clkdiv)

# Although it can still be added if the register is not the full data width
jtag.write_dr $dut.reg(:clkdiv), :size => 32

# A rich read method is available which supports bit-level read, store and overlay operations
jtag.read $dut.reg(:clkdiv)

# In cases where both shift in (TDI) and shift out data (TDO) are critical, (e.g. compare shift
#  out data on a write, or shfit in specific data on a read) the shift_in_data and 
#  shift_out_data options can be specified.  By default, TDO will be dont care on writes
#  and TDI will be 0 on reads.
jtag.write_dr $dut.reg(:clkdiv), :shift_out_data => 0x4321
jtag.read_dr $udt.reg(:clkdiv), :shift_in_data => 0x5678

# Similar methods exist for the instruction register
jtag.write_ir 0x1F, :size => 5
jtag.read_ir 0x1F, :size => 5

A secondary API provides low level control of the TAP Controller state machine.

jtag.pause_dr do
  jtag.shift_dr do
    # The shift method accepts the same arguments as the canned read/write methods
    jtag.shift 0x55, :size => 32

See the OrigenJTAG::Driver and OrigenJTAG::TAPController APIs for more details about the available driver methods.

Any model/controller within a target runtime environment can listen out for JTAG state changes by implementing the following callback handler:

def on_jtag_state_change(new_state)
  if new_state == :update_dr
    # Do something every time we enter this state

How To Setup a Development Environment

Clone the repository from Github.

An instance of the OrigenJTAG driver is hooked up to a dummy DUT object for use in the console:

origen i

> $dut.jtag
=> #<OrigenJTAG::Driver:0x0000001ee48e78>

Follow the instructions here if you want to make a 3rd party app workspace use your development copy of the OrigenJTAG plugin: Setting up a Plugin Development Environment

This plugin also contains a test suite, makes sure this passes before committing any changes!

origen examples