Platform opens two routes to DDR4 testing
Engineers designing with Double Data Rate 4 (DDR4) memory devices can quickly deploy tests for shorts and opens on control, address and data lines with the boundary scan test (BST) tools of ASSET InterTech’s ScanWorks platform for fast test and programming.
Downloadable models of DDR4 memory devices can be rapidly integrated into a ScanWorks Memory Access Verify (MAV) test action, which can then test the access to on-board DDR4 memory.
With the ScanWorks MAV test action, shorts and opens testing of DDR4 memory devices can begin with board prototypes in development and continue on to production units in manufacturing.
DDR4, the latest generation of this type of fast random-access memory, doubles the top-end data transfer speed of the former generation, DDR3, and consumes less power. DDR4 devices can perform 4,266 million transfers per second (MT/s) on a 1.2V power line. DDR3’s top transfer speed is 2,133MT/s with a 1.65V supply.
“We are starting to see more DDR4 memory show up in designs based on system-on-a-chip (SoC) devices, such as the Zynq UltraScale+,” said Michael Johnson, Product Manager for ScanWorks Boundary-Scan Test. “Our online library of DDR4 device models really simplifies the process of developing a ScanWorks MAV action for testing connectivity to these devices.”
ScanWorks actually supports two means of testing DDR4 devices. The MAV action facilitates DDR4 interconnect testing by accessing the memory array through low-speed emulation of normal read and write commands.
As such, this test mode can be employed without designing the circuit board to meet any specific design-for-test (DFT) considerations.
In addition, ScanWorks also supports a test mode that is built into DDR4 devices, Connectivity Test (CT). When activated, CT tests for shorts and opens by defining the response of chip output pins as a combinatorial function of stimulus at input pins.
CT has faster test run times and offers better coverage and more granular diagnostics of faults, but implementing it presupposes that particular DFT measures had been followed when components were selected and the board was designed.
When CT can be employed, ScanWorks DDR4 device models may be downloaded for use with the ScanWorks Component action.
CT and MAV are excellent means of providing fault coverage around DDR4 memory devices, however, these tests do not operate the DDR4 memory devices in their normal, at-speed functional mode.
To meet this need, the ScanWorks Processor-based Functional Test tool for DDR4 (PFTDDR) provides at-speed, functional test with structural diagnostics of DDR4 memory devices.
For a comprehensive test suite, PFTDDR can be run after MAV or CT tests.
PFTDDR differs from all other functional test applications in that it does not require a functioning operating system in order to test the integrity and functionality of the DDR memory, saving valuable time on the production line. PFTDDR includes nine robust memory tests to exercise DDR4 at-speed and under loaded conditions.
The non-intrusive nature of ScanWorks testing is well suited to many systems with DDR4 memory devices, since they often involve densely populated circuit boards with high-speed chip-to-chip interconnects.
For this type of circuit board, intrusive test technologies based on mechanical probes or bed-of-nails fixtures require physical access points, which can introduce signaling anomalies that compromise the integrity or reliability of memory function and thus invalidate certain test results. The combination of BST and PFTDDR supports robust test coverage and high test quality throughout the entire life-cycle of the product.