Improved Test Coverage Design for Testability

100% test coverage is what everyone strives for, but is extremely difficult and expensive to achieve. These suggestions will help anyone looking to add test coverage into their products using boundary-scan testing.

  • Use as many boundary-scan devices as possible (see boundary-scan chain tips)
  • Use buffers, data transceivers and other glue logic with boundary-scan capability (TI ABT, BCT families)

The ScanIO-300LV module provides a total of 300 fully bidirectional test channels with virtually unlimited memory depth per pin. Each line is independently controlled and can be individually configured as an input or output. During testing, the programming and control of the test channels is automatically performed by the ScanExpress™ tools without any user intervention. The voltage level of the I/O and JTAG interfaces is programmable from 1.25V to 3.3V and supports either single ended or low voltage differential (LVDS) signaling.

Improving Test Coverage
Improving Test Coverage

Through the use of boundary-scan technology, the ScanDIMM Tester provides fully bi-directional test signals. A boundary-scan Test Access Port (TAP) connects to a host computer which provides virtually unlimited memory depth for testing each of the DIMM socket(s) pins.

Improving Test Coverage

Transceiver Testing

Improving Test Coverage

Loopback Cables

Improving Test Coverage

Cluster Testing

Clock Oscillators

  • Single Alternating Test Vector
  • Use Re-run Test Step if Failed Option in ScanExpress Runner

Real Time Clocks

  • Two separate cluster tests
  • 1st cluster test sets the seconds register on RTC
  • 2nd cluster test reads and compares the seconds register after a specific amount of time
  • Use Stop on Last Test Vector and Wait Option in ScanExpress Runner on 1st cluster test


  • Setting and reading UART registers
  • Loopback testing TXD/RXD lines

RS-232 / RS-485 Transmitters / Receivers

  • Loopback testing TXD/RXD lines

Logic Gates

  • Simple truth table based on inputs and outputs


  • Can be performed as a stand-alone test or loopback
  • Cluster test sets the DAC value and analog meter takes measurement
  • Analog source sets the ADC value and boundary-scan compares result
  • Reliable testing for MSB data pins within device accuracy

SPI / I2C Devices

  • Complete control of device functionality

NAND and XOR Tree

  • Every pin must be controllable by a JTAG device

LEDs & Lamps

  • Visual Inspection

Script Testing

Scripting is more flexible than Cluster tests

  • Using C-like language and many C-like functions
  • Read and write to/from files
  • Use of loops and conditions based on results of tests
  • Store global variables to use in another (or later) script test
  • Use of sub-routines and/or include functions
  • Easy way of reusing existing functions