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12.4 EVM Firmware — Introduction
The reference firmware that is provided with the EVM is intended to demonstrate basic phase-shifted full-
bridge DC-DC converter functionality, as well as some basic PMBus communication and primary-to-
secondary communication. The firmware is used as an initial platform for particular applications. This
section provides a brief introduction to the firmware.
12.4.1
Firmware Infrastructure overview
The firmware includes one startup routine and three program threads. The startup routine initializes the
controller setup for the targeted operation functions or status. Please contact TI for detailed initialization
information.
As shown in
Figure
interrupt request (IRQ); and (3) the background loop. These threads are described as:
1. Fast Interrupt (FIQ)
•
Critical or time-sensitive tasks are within the FIQ. Functionally, FIQ events are the highest priority
and are addressed as soon as possible.
2. Timer Interrupt (IRQ)
•
The majority of the firmware tasks occur during the IRQ. IRQ events occur synchronously every
100 µs.
3. Background Loop
•
Non time-sensitive tasks are implemented in the background loop. Background Loop items are
addressed whenever FIQ and IRQ events are not handled.
4 Switching
Cycle Timer
12.4.2
Tasks Within FIQ
FIQ events have the highest priority and are addressed as soon as possible. The FIQ includes critical and
time-sensitive tasks. The firmware included with the EVM includes two functions called by the FIQ:
•
Constant Power and Constant Current
•
Cycle-by-cycle current limit
The FIQ interrupt is called to respond every four switching cycles.
SLUUAK4 – August 2013
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34, the three program threads are (1) the fast-interrupt request (FIQ); (2) the timer-
FIQ
Complete
Background
Loop
Figure 29. Firmware Structure Overview
Copyright © 2013, Texas Instruments Incorporated
Description of the Digital Phase-Shifted Full-Bridge Converter
FIQ
FIQ
Complete
4 Switching
Cycle Timer
100Ûs
Timer
IRQ
Complete
IRQ
Using the UCD3138PSFBEVM-027
33
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