PXS20RM Datasheet, PDF (61/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Introduction
1.4.35 Cross Triggering Unit (CTU)
The ADC cross triggering unit allows automatic generation of ADC conversion requests on user selected
conditions without CPU load during the PWM period and with minimized CPU load for dynamic
configuration.
The CTU implements the following features:
• Cross triggering between ADC, PWM, eTimer, and external pins
• Double buffered trigger generation unit with as many as 8 independent triggers generated from
external triggers
• Maximum operating frequency less than or equal to 120 MHz
• Trigger generation unit configurable in sequential mode or in triggered mode
• Trigger delay unit to compensate the delay of external low pass filter
• Double buffered global trigger unit allowing eTimer synchronization and/or ADC command
generation
• Double buffered ADC command list pointers to minimize ADC-trigger unit update
• Double buffered ADC conversion command list with as many as 24 ADC commands
• Each trigger capable of generating consecutive commands
• ADC conversion command allows control of ADC channel from each ADC, single or synchronous
sampling, independent result queue selection
• DMA support with safety features
1.4.36 Cyclic Redundancy Checker (CRC) Unit
The CRC module is a configurable multiple data flow unit to compute CRC signatures on data written to
its input register.
The CRC unit has the following features:
• 3 sets of registers to allow 3 concurrent contexts with possibly different CRC computations, each
with a selectable polynomial and seed
• Computes 16- or 32-bit wide CRC on the fly (single-cycle computation) and stores result in
internal register.
The following standard CRC polynomials are implemented:
— x¹⁶ + x¹² + x⁵ + 1 [16-bit CRC-CCITT]
— x³² + x²⁶ + x²³ + x²² + x¹⁶ + x¹² + x¹¹ + x¹⁰ + x⁸ + x⁷ + x⁵ + x⁴ + x² + x + 1
[32-bit CRC-ethernet(32)]
• Key engine to be coupled with communication periphery where CRC application is added to allow
implementation of safe communication protocol
• Offloads core from cycle-consuming CRC and helps checking configuration signature for safe
start-up or periodic procedures
• CRC unit connected as peripheral bus on internal peripheral bus
• DMA support
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
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