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8.1
PTV Compensated Buffers
8.2
I/O Timings
8.3
External Terminators
9
Peripheral Section
Peripheral Section
The impedance of I/O buffers is affected by process, temperature and voltage. For some interfaces, these
impedance changes can make it difficult to meet specifications across the full range of these parameters.
For that reason, the TCI6482 uses PTV (process, temperature, voltage) compensated I/O buffers for
critical interfaces. The PTV compensation works by adjusting internal impedances to nominal values
based on external reference resistances. The interfaces that use PTV compensated I/O buffers and the
details on the reference resistances are given in
Table 10
.
Table 10. PTV Compensated Interfaces
Interface
Operating Voltage
Reference Resistance
PCI
3.3V (DVDD33)
39 ohm resistor from RSV15 to GND
20 ohm resistor from RSV16 to DVDD33
RGMII
1.5V or 1.8V (DVDD15)
200 ohm resistor from RSV13 to GND
200 ohm resistor from RSV14 to DVDD15
DDR2
1.8V (DVDD18)
200 ohm resistor from RSV11 to GND
200 ohm resistor from RSV12 to DVDD18
The resistors used can be standard 5% tolerance.
The I/O timings in the TCI6482 data manual are given for the tester test load. These timings need to be
adjusted based on the actual board topology. In general, datasheet timings for interfaces that existed on
the TCI100 device have remained the same. However, some differences exist. Refer to the datasheet for
details. Since the TCI6482 is a completely new device, the nominal timings may be different than the
TCI100 and the I/O buffers may perform differently with a particular board topology. For these reasons, it
is highly recommended that timing for all high speed interfaces (with the exception of DDR and SRIO) on
a TCI6482 design be checked using IBIS simulations. For more details on performing IBIS simulations
see, Using IBIS Models for Timing Analysis (
SPRA839
).
The clock for many peripherals is generated by a divide down from the CPU core clock. Since the CPU
core clock is different than the TCI100, the divider and timings should be checked. This impacts the
McBSP, EMIFA and Timer Peripherals.
The TCI6482 input/output (I/O) buffers have been modified for the new manufacturing process and have a
different output impedance than those of the TCI100. For boards designed with the TCI100, termination
resistor values should be checked by running IBIS simulations.
Series impedance is not always needed but is recommended for some interfaces to avoid
over-shoot/under-shoot problems. Check the recommendations in the Peripherals chapters and/or perform
IBIS simulations on the interface.
This section covers each of the TCI6482 peripherals/modules. This section is intended to be used in
addition to the information provided in the TCI6482 data manual, the Module Guides provided for each of
the peripherals and relevant application notes. The 4 types of documents should be used as follows:
•
Data Manual: AC Timings, Register Offsets
•
Module Guide: Functional Description, Programming Guide
•
Applications Notes: System level issues
•
This Chapter: Configuration, System level issues not covered in a separate application note,
Differences to the TCI100
Each peripheral section includes recommendations on how to handle pins on interfaces that are disabled
or for unused pins on interfaces that are enabled. Generally, if internal pull-ups or pull-downs are included
the pins can be left floating. Any pin that is output only can always be floated. If internal pull-ups and
22
TMS320TCI6482 Design Guide and Migration from TMS320TCI100
SPRAAC7B – April 2006
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