TXC-06880BIOG Transwitch Corporation, TXC-06880BIOG Datasheet - Page 20

• Manufacturer Part Number: TXC-06880BIOG
• Manufacturer: Transwitch Corporation

Specifications of TXC-06880BIOG

• Operating Supply Voltage (typ): 1.8/3.3V
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Not Compliant

Envoy-CE2 Device
DATA SHEET
TXC-06880
2 0 o f 12 2
2.1.9.1 Boundary Scan Operation
2.1.9.2 Boundary Scan Reset
Test Mode Reset (TRST). The output signal is Test Data Output (TDO). In addition to the TAP,
a pin is provided (DEVHIZ) to place the output buffers in a high impedance state for systems
that do not support the IEEE 1149.1 standard. Boundary scan signal timing is shown in
20.
The TAP controller receives external control information via a Test Clock (TCK) signal and a
Test Mode Select (TMS) signal, and sends control signals to the internal scan paths. Detailed
information on the operation of this state machine can be found in the IEEE 1149.1 standard.
The serial scan path architecture consists of an instruction register, a boundary scan register
and a bypass register. These three serial registers are connected in parallel between the Test
Data Input (TDI) and Test Data Output (TDO) signals, as shown in
The boundary scan function can be reset and disabled by holding lead TRST low. When
boundary scan testing is not being performed the boundary scan register is transparent,
allowing the input and output signals to pass to and from the Envoy-CE2 device’s internal
logic. During boundary scan testing, the boundary scan register may disable the normal flow
of input and output signals to allow the device to be controlled and observed via scan
operations.
The Envoy-CE2 supports the following boundary scan test instructions:
Specific control of the TRST lead is required in order to ensure that the boundary scan logic
does not interfere with normal device operation. This lead must either be held low, asserted
low, or asserted low then high (pulsed low), to asynchronously reset the Test Access Port
(TAP) controller during power-up of the Envoy-CE2. If boundary scan testing is to be
performed and the lead is held low, then a pull-down resistor value should be chosen which
will allow the tester to drive this lead high, but still meet the V
Input, Output and Input/Output Parameters section of this Data Sheet for worst case leakage
currents of all devices sharing this pull-down resistor.
The EXTEST test instruction provides the ability to test the connectivity of the Envoy-
CE2 device to external circuitry.
The SAMPLE/PRELOAD test instruction provides the ability to examine the values of
the Input and Output pins without interfering with device operation, and to initialize the
Boundary Scan Register with new values for the next operation.
The BYPASS test instruction provides the ability to bypass the Envoy-CE2 boundary
scan and instruction registers.
The IDCODE test instruction provides a unique device identification for the Envoy-CE2
device.
The HIGHZ test instruction provides the ability to drive all 3-state outputs and bidirec-
tional pins to their high impedance state.
The CLAMP test instruction provides the ability to drive the component pins of the chip
from the boundary scan register, while the bypass register is selected as the serial path
between TDI and TDO. The component pins will not switch while the CLAMP instruction
is selected.
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Functional Description
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PRELIMINARY TXC-06880-MB, Ed. 4
IL
Figure
requirements listed in the
9.
February 2005
Figure