IDT88K8483 Integrated Device Technology, IDT88K8483 Datasheet - Page 73

• Manufacturer Part Number: IDT88K8483
• Description: Spi-4 Exchange Document Issue 1.0
• Manufacturer: Integrated Device Technology

that the chip operates properly. This can be done in one of the three different ways:
Once in the Test-Logic-Reset test, the JTAG logic will remain in this state as long as TMS is high, regardless of the state of TRSTB.
parts from different vendors may present significant loading to the controller. To compensate for this, the designer should include buffers on TMS,
TRSTB and TCK to account for unknown device impedance. For systems with several components, the designer should use a high fan-out buffer.
IDT IDT88K8483
The internal JTAG logic of each device powers up in an unknown state, so it is necessary at power-on to reset it to the Test-Logic-Reset state so
1.
2. A low pulse is applied to TRSTB at power on as shown in
3. TCK can be clocked five or more times while TMS is held high. In this case, TRSTB can be pulled high. This method is also appropriate if the
The TRSTB signal is an option reset pin and may not be available on all JTAG test connectors. TRSTB should be held high during JTAG testing.
The TCK signal should be carefully routed on board according to standard layout design to minimize skew and noise problems.
JTAG specifications require that pull-up resistors be supplied internally to the TDI, TRSTB, and TMS pins in the chips. Very long JTAG chains or
testing.
edge is not required on TRSTB. TRSTB can then be held high as long as TMS is also pulled high, thereby keeping the logic in the reset state.
This method is appropriate if the JTAG tester does not drive TRSTB.
JTAG tester does not have TRSTB.
TRSTB is pulled low by a resistor. TRSTB must also connect to the JTAG connector, and the JTAG tester must drive TRSTB high for JTAG
JTAG Connector
TDO
TRSTB
TMS
TCK
TDI
TRSTB
TMS
TCK
VDD
VDD
Figure 40 TRSTB Signal During Power-On Reset
TRSTB
Figure 39 JTAG Daisy Chain
TMS
TCK
Figure 40 TRSTB Signal During Power-On Reset
IDT88K8483 - 1
TRSTB
TCK
73 of 162
TMS
TDI
JTDO
TRSTB
TMS
TCK
IDT88K8483 - 2
TDI
TCK
TMS
TRSTB
TDO
p.73. Note that a falling
October 20, 2006