PXR40RM Datasheet, PDF (50/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Introduction
1.2.10 Periodic interrupt timer (PIT)
The periodic interrupt timer (PIT) is an array of timers that can be used to generate interrupts and trigger
DMA channels. It also provides a dedicated real-time interrupt timer (RTI), which runs on a separate clock
and can be used for system wake-up.
The following features are implemented:
• Four independent timer channels
• Each channel includes 32-bit wide down counter with automatic reload
• Three channels clocked from system clock
• One channel clocked from crystal clock (wake-up timer)
• Wake-up timer remains active when system enters stop mode. Used to restart system clock after
predefined time-out period
• Each channel can optionally generate interrupt request when timer reaches zero
• Channels can optionally produce trigger event when timer reaches zero (used to trigger eQADC
queues)
1.2.11 System timer module (STM)
The system timer module (STM) is a 32-bit timer designed to support commonly required operating
system and application software timing functions. The STM includes a 32-bit up counter and four 32-bit
compare channels with a separate interrupt source for each channel.
The following features are implemented:
• One 32-bit up counter with 8-bit prescaler
• Four 32-bit compare channels
• Independent interrupt source for each channel
• Counter can be stopped in debug mode
1.2.12 Enhanced queued analog to digital converter (eQADC)
The enhanced queued analog to digital converter (eQADC) block provides accurate and fast conversions
for a wide range of applications. The two eQADCs on the PXR40 provide a parallel interface to four
on-chip analog to digital converters (ADC), and a single-master to single-slave serial interface to an
off-chip external device.
The ADCs include features designed to allow the direct connection of high impedance acoustic sensors
that might be used in a system for detecting engine knock. These features include differential inputs;
integrated variable gain amplifiers for increasing the dynamic range; programmable pullup and pulldown
resistors for biasing and sensor diagnostics.
eQADC_B also integrates four programmable decimation filters capable of taking in ADC conversion
results at a high rate, passing them through a hardware low-pass filter, then down-sampling the output of
the filter and feeding the lower sample rate results to the result FIFOs. This allows the ADCs to sample
the sensor at a rate high enough to avoid aliasing of out-of-band noise, while providing a reduced sample
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PXR40 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor