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Advance Data Sheet
T7633 Dual T1/E1 3.3 V Short-Haul Terminator
May 1998
138
Lucent Technologies Inc.
JTAG Boundary-Scan Specification
(continued)
Instruction Register
The instruction register (IR) is 4 bits in length. Table 63 shows the BS instructions implemented by the T7633.
Table 63. T7633’s Boundary-Scan Instructions
The instructions not supported in T7633 are INTEST, RUNBIST, TOGGLE. A fixed binary 0001 pattern (the 1 into
the least significant bit) is loaded into the IR in the capture-IR controller state. The IDCODE instruction (binary
0001) is loaded into the IR during the test-logic-reset controller state and at powerup.
The following is an explanation of the instructions supported by T7633 and their effect on the devices' pins.
EXTEST:
This instruction enables the path cells, the pins of the ICs, and the connections between ASICs to be tested via the
circuit board. The test data can be loaded in the chosen position of the BS register by means of the SAMPLE/PRE-
LOAD instruction. The EXTEST instruction selects the BS register as the test data register. The data at the function
inputs is clocked into the BS register on the rising edge of TCK in the CAPTURE-DR state. The contents of the BS
register can be clocked out via TDO in the SHIFT-DR state. The value of the function outputs is solely determined
by the contents of the data clocked into the BS register and only changes in the UPDATE-DR state on the falling
edge of TCK.
IDCODE:
Information regarding the manufacturer’s ID for Lucent, the IC number, and the version number can be read out
serially by means of the IDCODE instruction. The IDCODE register is selected, and the BS register is set to normal
mode in the UPDATE-IR state. The IDCODE is loaded at the rising edge of TCK in the CAPTURE-DR state. The
IDCODE register is read out via TDO in the SHIFT-DR state.
HIGHZ:
All 3-statable outputs are forced to a high-impedance state, and all bidirectional ports to an input state by means of
the HIGHZ instruction. The impedance of the outputs is set to high in the UPDATE-IR state. The function outputs
are only determined in accordance with another instruction if a different instruction becomes active in the UPDATE-
IR state. The BYPASS register is selected as the test data register. The HIGHZ instruction is implemented in a sim-
ilar manner to that used for the BYPASS instruction.
SAMPLE/PRELOAD:
The SAMPLE/PRELOAD instruction enables all the inputs and outputs pins to be sampled during operation (SAM-
PLE) and the result to be output via the shift chain. This instruction does not impair the internal logic functions.
Defined values can be serially loaded in the BS cells via TDI while the data is being output (PRELOAD).
Instruction
Code
Act. Register
TDI
→
TDO
Boundary Scan
Mode
Function
Output Defined Via
EXTEST
0000
TEST
Test external
connections
Read Manuf.
Register
3-state
Sample/load
Min. shift path
—
BS Register
IDCODE
0001
Identification
NORMAL
Core Logic
HIGHZ
0100
0101
1111
—
BYPASS
Boundary Scan
BYPASS
BYPASS
X
Output — High Impedance
Core Logic
Core Logic
Output — High Impedance
SAMPLE/PRELOAD
BYPASS
EVERYTHING ELSE
NORMAL
NORMAL
X