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Overview for 1149.1 Initialization Process. April 27, 2010. Configurable I/O. Since the original development of the 1149.1 Boundary Scan standard, the complexity and variation of I/O cells as well as the ICs themselves has greatly increased in the digital IC industry

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configurable i o
Configurable I/O
  • Since the original development of the 1149.1 Boundary Scan standard, the complexity and variation of I/O cells as well as the ICs themselves has greatly increased in the digital IC industry
  • Process technology advancements have reduced the safe operating voltage ranges of transistors
  • I/Os are now configurable for the electrical characteristics such as power levels, drive strength, VIL/VIH, impedance, etc.
  • Unused I/O may be configured to be power downed and to not actually be capable of receiving logic values placed on the pin for lower power modes
  • In both mission and test modes, I/Os frequently require configuration before they can be used
boundary scan operation failures
Boundary Scan Operation Failures
  • I/O cannot correctly drive or receive a logic 1 or 0 until the correct configuration for the given instance is loaded and known
  • Mismatched configurations of I/Os on a board could cause a driven logic 1 to be received as a logic 0
  • In mission mode, a powered-off I/O analog cell cannot SAMPLE the pin value to the BSR
  • Until an Initialization Procedure is completed to program or configure the I/O, none of 1149.X instructions which control or observe the pins can be reliably depended on to correctly operate
ic initialization for safe operation for board level interconnect test
IC Initialization for “Safe” operation for Board-level Interconnect Test
  • It may be desirable or necessary to place an IC into a “safe” mode during Board-level tests
  • If board interconnect tests are performed before attachment of heat sinks, it may be necessary to power down large portions of IC core for thermal management
  • To reduce power consumption, PLLs may need to be disabled during board level interconnect testing
  • Without setting the I/O voltage level program correctly, incorrect applied input signal voltage may permanently damage an I/O cell
  • Chips with Secure information may require the deletion of data before Boundary operations
initialization procedure
Initialization Procedure
  • All of these issues can be resolved by Initialization procedure
  • The proposed Initialization procedure support needs to allow for the following:
    • Optional parameterized configuration by setting data in a TDR (INIT_DATA)
    • Optional specification a minimum number of TCKs (or other time value) for configuration completion to take effect (either for a state machine execution or a “settling time”)
    • Option to receive status bits
    • Option to “poll” for earlier completion
    • Control of when the mission mode is disrupted
  • 2 instructions:
    • INIT_SETUP (optional INIT_DATA TDR)
    • INIT_RUN (optional INIT_STATUS TDR)
    • Run after POR, before EXTEST
    • NOT dependent on RTI TAP state
  • BSDL to document the data fields of INIT_DATA) with optional mnemonics for field values, Completion time, and optional expected results (format, content TBD)
  • Side file to specify per chip instance initialization data and expected results
board test control of chip state during test
Board Test Control of Chip State During Test
  • Board tests consist of series of 1149.1 based tests
  • Each test starts and ends at Test-Logic-Reset during potential glitching of TRST* during transition between tests
  • Need for a some optional persistence of a “Test Safe” state after a Test-Logic-Reset and before a normal mission-mode reset
  • The INIT_DATA values can be re-usable


  • The Test Safe state should tend to persist
modes of usages
Modes of Usages
  • Initialization can be used under different types of usages across different chips on the same Boundary scan chain at the board level
    • No Initialization required (Chips stay in BYPASS)
    • Direct Parameterization: with INIT_SETUP only, followed by EXTEST (No Completion Time requirement)
    • Simple State Machine Execution: INIT_RUN only with Completion Time required followed by EXTEST (No parameterization required)
    • Parameterized State Machine Execution: Initialization with INIT_SETUP for parameterization, then INIT_RUN for Completion Time before EXTEST
bsdl updates for initialization
BSDL Updates for Initialization
  • BSDL will have new Attributes and Keywords for Initialization
  • Create REGISTER_MNEMONICS Attribute to describe optional mnemonics for data fields
  • Create REGISTER_FIELDS to define the subfields of the INIT_DATA or INIT_STATUS register sub-fields
side file
Side file
  • The side file is specific to each instantiation of chip supporting Initialization on the board
  • Side file would provide the parameterization required per instance
  • Side file would facilitate tool inter-operability
  • Based in based PDL constructs from P1687
  • File supplies the data values for the INIT_DATA values
initialization flow
Initialization Flow
  • UpdateIR INIT_SETUP on chips which support it; other chips are in BYPASS
  • ShiftDR INIT_DATA TDR to set parameters
    • Parameters can control the electrical settings of the I/Os per board specifics
    • IOs may support a wide range of electrical settings which may not be able to signal correctly without initialization
    • Parameters can control system internals as well. e.g. power-downs, PLL Kill, etc. for safe operation
initialization flow1
Initialization Flow
  • PRELOAD instruction should be run before INIT_RUN to initialize the data path values
  • At UpdateIR, INIT_RUN starts execution to place chip in state ready for EXTEST*
    • Intrusive
  • Internal state machines may be executing for a Completion time to do the state changes
  • ShiftDR will shift either optional INIT_STATUS or BYPASS TDR
  • The board must wait until last chip has completed
    • Completion is define by either a Completion time or by a Done Status provided by INIT_STATUS TDR


Initial TAP State



Some chips in BYPASS mode;

chip state undisturbed



Load INIT params per chip

as needed into INIT_DATA

UpdateIR / ShiftDR


Initialize the data values into

the BSR

flow con t
Flow (Con’t)

Invasive; FSM starting running

if any chips need it



Initialization operating (not TLR)

Any State of TAP



Some chips in BYPASS mode;



After max Completion Time or

INIT_STATUS Done indicated

EXTEST operation with correct

data and electrical values