GitHub repository: https://github.com/daxzio/cocotbext-jtag

JTAG simulation models for cocotb.

Installation from pip (release version, stable):

$ pip install cocotbext-jtag

Installation from git (latest development version, potentially unstable):

$ pip install https://github.com/daxzio/cocotbext-jtag/archive/main.zip

Installation for active development:

$ git clone https://github.com/daxzio/cocotbext-jtag
$ pip install -e cocotbext-jtag

See the tests directory for complete testbenches using these modules.

The JTAGBus is used to map to a JTAG interface on the dut. These hold instances of bus objects for the individual channels, which are currently extensions of cocotb_bus.bus.Bus. Class methods from_entity and from_prefix are provided to facilitate signal default name matching.

• tck
• tms
• tdi
• tdo

• trst

The JTAGDriver class implement a JTAG driver and is capable of generating read and write operations against JTAG devices, either singularly or in a chain.

To use these modules, import the one you need and connect it to the DUT:

from cocotbext.jtag import JTAGDriver, JTAGBus

bus = JTAGBus(dut)
jtag_driver = JTAGDriver(bus)

The first argument to the constructor accepts an JTAGBus object. These objects are containers for the interface signals and include class methods to automate connections.

Once the module is instantiated, read and write operations can be initiated in a couple of different ways.

• period: Clock frequency period of tck, default 100
• units: Clock units, default ns
• logging_enabled: Logging enable, default True

• add_device(device): Add device to jtag chain, must be of type JTAGDevice
• set_reset(num): Reset for num if trst is present in JTAGBus, raise warning if trst is not present
• reset_finished(): Asyn wait until reset is finished
• reset_fsm(): Send 5 tck pulses while tms is held high in JTAGBus, this resets the finite state machine inside a JTAG TAP
• send_val(addr, val, device, write): Send addr to device (default: 0). The val is used to write if write is True or verify against if write is False
• write_val(addr, val, device=0): Write val to addr of device (default: 0).
• read_val(addr, val=None, device=0): Read from addr of device (default: 0). If val present verify against returned value.
• read_idcode(device): Read device number device and confirm it matched the IDCODE set for that device

from cocotbext.jtag import JTAGDevice

class J1JTAGDevice(JTAGDevice):
    def __init__(self, name='jtaglet1', idcode=0x53817905, ir_len=5):
        super().__init__(name, idcode, ir_len)
        self.add_jtag_reg('USERDATA', 32, 0x8)
        self.add_jtag_reg('USEROP', 8, 0x9)

from cocotbext.jtag import JTAGDriver
from cocotbext.jtag import JTAGBus

class testbench:
    def __init__(self, dut):
        bus = JTAGBus(dut)
        self.jtag = JTAGDriver(bus)
        self.jtag.add_device(J1JTAGDevice())