% render "layouts/basic.html" do

%# HTML tags can be embedded in mark down files if you want to do specific custom
%# formatting like this, but in most cases that is not required.
<h1><%= Origen.app.namespace %> <span style="font-size: 14px">(<%= Origen.app.version %>)</span></h1>

### Purpose

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](http://origen-sdk.org/nexus/).

### How To Import

In your Gemfile add:

~~~ruby
gem "origen_jtag", ">= <%= Origen.app.version %>"
~~~

or if your application is a plugin add this to your <code>.gemspec</code>

~~~ruby
spec.add_development_dependency "origen_jtag", ">= <%= Origen.app.version %>"
~~~

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

### How To Use

Include the <code>OrigenJTAG</code> 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 <code>jtag</code> method which will return an instance of
[<code>OrigenJTAG::Driver</code>](<%= path "api/OrigenJTAG/Driver.html" %>).

The following attributes can be customized by defining a <code>JTAG_CONFIG</code>
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:

~~~ruby
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)
  JTAG_CONFIG = {
    :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
  end

end

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.

~~~ruby
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
$dut.reg(:clkdiv).bits(:div).read(0x55)
jtag.read $dut.reg(:clkdiv)
# 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.

~~~ruby
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
  end
end
~~~

See the [<code>OrigenJTAG::Driver</code>](<%= path "api/OrigenJTAG/Driver.html" %>) and
[<code>OrigenJTAG::TAPController</code>](<%= path "api/OrigenJTAG/TAPController.html" %>)
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:

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


### How To Setup a Development Environment

[Clone the repository from Github](https://github.com/Origen-SDK/origen_jtag).

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](http://origen-sdk.org/origen/latest/guides/plugins)

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

~~~
origen examples
~~~

<%= disqus_comments %>

% end