2. What is this BST all about
• Standalone BST on the Microchip PIC32 MPU. Running under
Lorenzo Electronics LE1201 BST Controller, test program
performs short-tests for the BST worthy MPU pins.
• For the MPU pins with both input and output boundary scan
(BSC) cells, BST Controller will setup output BSC cells to
drive the MPU pins. Moments later, MPU pins logic level will
be captured via input BSC cells and sent back to the host test
controller. BST Controller examines the test results and records
detailed test information.
• System features facilitate expedited test execution. MPU pins
under test are partitioned into multiple groups. Each group will
have test patterns of single logic 1 bit rotating among all other
logic 0 bits. With that, MPU pins short-circuit defects can be
detected. All the pin groups test runs are done in parallel.
• Fault insertion test will be executed. It illustrates Lorenzo
Electronics LE1201 BST Controller fault detection capability
and its detailed data log useful for debug purpose.
Lorenzo Electronics, LLC 2
3. JTAG setup: Standalone BST on PIC32 MPU
• In this test, JTAG 1149.1 standard conforming Microchip
PIC32 MPU (U1, left) runs BST interacting with a JTAG
controller pictured on the right. Externally, JTAG controller
is connected to PC via a USB cable.
• A 14-wires ribbon cable connects the JTAG controller to the
14-pin JTAG header on the MPU board. Single blue wire
connects +3.3v dc power to the JTAG controller, which can
operate on voltage level as low as 1.8v.
URL for Microchip Explorer 16 Development Board User's Guide:
http://ww1.microchip.com/downloads/en/DeviceDoc/50001589b.pdf
Lorenzo Electronics, LLC 3
4. snippet of sysout file listing JTAG port tdi/tdo data
• LE1201 BST controller runs test executing user-defined,
device-specific test programs. Each test program is divided
into a number of test patterns. In that, each test pattern is made
of driving data and expected data. Expected data will be
compared to the BST received tdo data stream to determine the
test results and record BSC pin fault(s), if any.
• BST execution sysout file lists JTAG port's tdi/tdo pins raw i/o
data streams for each test pattern. JTAG controller originated
data stream: tdi will be latched into MPU BSC output cells to
Lorenzo Electronics, LLC 4
5. drive the MPU pins. JTAG port stream: tdo, MPU sourced,
contains BSC input cells states that reflect MPU pins logic
levels. Normally, an MPU pin's input cell should mirror its
output cell's logic level.
• LE1201 BST controller execute each BST test pattern with the
same TAP state machine cycle – starting from Test/Idle state,
followed by Capture-DR, Shift-DR, Update-DR, and back to
Test/Idle state. In this state machine cycle, BSC registers are
“clocked” in the order of CAPTURE (input cell registers),
SHIFT (tdi stream in / tdo stream out), and UPDATE (output
cell registers). With that, BST driving data has its effects
delayed by one test pattern.
• In the sysout file, tdi and tdo data blocks listed in hexadecimal
numbers are representing digits serially shifted in and out of the
MPU JTAG pins - per test pattern. For the Microchip MPU
chip, the total number of BSC cells is 237 with cell index
ranging from 0 to 236.
• Sysout file tdi/tdo data blocks have the 4 LSB bits' (cell 0-3)
hex number listed on the lower right side. BSC cells indexing
are defined in the MPU's BSDL file.
Lorenzo Electronics, LLC 5
6. Snippet of a BST output file (*.csv)
• Record detailed BSC output/ctrl cells driving logic states and
captured input cells logic states for all the test patterns.
• Highlighted spreadsheet column C shows MPU pin 25 (port
name: RB0, output/ctrl cells, #177 and #178 respectively)
driving logic states (LE1201 conventions: 0, 1, or Z).
• Spreadsheet column B records MPU pin 25 input cell captured
logic states (LE1201 conventions: H or L).
• For MPU pin 25, test pattern #2 driving state of 1 (column C)
can be detected as H (column B) in test pattern #3.
• This BST passes the test. There is no “fail” label embedded in
the spreadsheet.
Lorenzo Electronics, LLC 6
7. Standalone BST on PIC32 MPU – w/ Fault Insertion
• With MPU pin 25 shorted to GND, this BST test repeats the
same test program as that in page 3.
Lorenzo Electronics, LLC 7
8. snippet of sysout file listing JTAG port tdi/tdo data – Failed
• This sysout file print out the BST failed message: Pattern 3,
failed device(s): [u1].
• Highlighted TDO data byte, with BSC cell index 176 to 183,
has hex value of b6. In contrast, corresponding pattern 3 TDO
data byte in page 4 has hex value of b7. It indicates that this
test's TDO stream has its bit with cell index #176 reset to 0.
• Note: TDO mask bit stream with cell index #176 has the bit
value of 1. For that, the corresponding TDO data bit will have
its bit value validated via comparing to the expected test result.
Lorenzo Electronics, LLC 8
9. Snippet of a BST output file (*.csv) – Failed
• This spreadsheet file records that MPU pin 25 (port name:
RB0, BSC cell index: 176) failed the BST in pattern #3 and
#17. The measured logic levels are all “L”.
Lorenzo Electronics, LLC 9
