REDMOND, Wash. Boundary scan was invented to ease testing of circuit boards, but Data I/O proposes to use it for programming. The company has teamed with JTAG Technologies B.V. (Geneva) to offer an inexpensive ($20,000) boundary-scan-based PLD programmer that can accelerate production, decrease inventory-tracking overhead and offload expensive ATE from programming duties.
Boards equipped with boundary scan can now have their programmable-logic devices programmed in place after they are already soldered down. Inventories need be kept of only unprogrammed parts, with the latest revisions automatically programmed on-board after passing the board through automatic test equipment.
Data I/O's BoundarySite programming system consists of a PCI-bus card for a PC plus software and a pod for connecting up to four boards for simultaneous testing. The five-prong connector attaches to the board to be tested, and the software programs all the PLDs on it.
Boundary scan, now an IEEE standard (IEEE 1149.1), works by including extra circuitry on critical chips, especially the microprocessor and associated ICs. This additional circuitry is mainly a daisy chain of buffers that isolate all off-chip connections at the "boundaries" of the package. Then lateral connections between adjacent buffers connect them into a long shift register, along with control logic for managing the boundary-scan circuitry.
ICs are put into a special mode whereby BoundarySite can load and read that long shift register, essentially "stuffing" any desired sequential operations into the data flow of the board's normal processing. In particular, BoundarySite stuffs the necessary data and instructions into the shift register to program the on-board complex PLDs.
Data I/O, long a leader in off-board PLD programmers, took a one-third equity share in JTAG Technologies to secure its deal to OEM the BoundarySite system under its own name.
"JTAG Technologies has pioneered boundary scan for programming PLDs in Europe. It just made sense for us to team with them rather than develop our own technology from scratch," said product marketing manager Ray Dellecker. "Now, with one stop at Data I/O, you can get the tools for off-board or on-board programming."
Traditionally, PLDs have been programmed off-board before being soldered down, permitting them to be tested ahead of time, but necessitating an inventory-control system to track versions and revisions to programming specs.
In addition, older boards often require off-board programming, because they are not equipped with the necessary boundary-scan board circuitry.
Many newer board designs are taking advantage of boundary-scan circuitry as a necessary evil a little bit of extra board space saves a lot of testing headaches. Boundary scan requires adding four on-board lines: input to the shift register, output from the shift register, clock and enable.
In designing a new board, one can add a fifth line, patented by Data I/O, called "autowrite," which will double the throughput of programming flash memories by halving the number of times the shift register has to be loaded. Instead of loading the shift register with flash-write enable high and then loading it identically again except taking flash-write low, the shift register is merely loaded once and the fifth autowrite line is strobed.
"Then you can program flash memories as fast as they can be programmed off-board about 30 seconds for a 16-Mbit flash memory," said Dellecker.
The technique integrates programming with manufacturing. So does using ATE to program devices on-board, but that slows the production line. "We estimate that one-third of the ATE's time might be spent on programming, so installing our equipment would offload expensive ATE from those programming tasks and thereby increases ATE throughput by one-third," said Dellecker.
Motorola proved the concept for Data I/O at its Swindon, U.K., cell-phone division. Motorola designed a circuit board containing three separate boundary-scan shift registers using 35 PLDs and flash-memory devices. "We were already using boundary scan to test boards," said Peter Collins, senior test development engineer. Now it is pressed into service for programming, too.