SPNS174
–
SEPTEMBER 2011
5.4
Enhanced High-End Timer (N2HET)
The N2HET is an advanced intelligent timer that provides sophisticated timing functions for real-time
applications. The timer is software-controlled, using a reduced instruction set, with a specialized timer
micromachine and an attached I/O port. The N2HET can be used for pulse width modulated outputs,
capture or compare inputs, or general-purpose I/O.. It is especially well suited for applications requiring
multiple sensor information and drive actuators with complex and accurate time pulses.
5.4.1
Features
The N2HET module has the following features:
•
Programmable timer for input and output timing functions
•
Reduced instruction set (30 instructions) for dedicated time and angle functions
•
160 words of instruction RAM protected by parity
•
User defined number of 25-bit virtual counters for timer, event counters and angle counters
•
7-bit hardware counters for each pin allow up to 32-bit resolution in conjunction with the 25-bit virtual
counters
•
Up to 32 pins usable for input signal measurements or output signal generation
•
Programmable suppression filter for each input pin with adjustable limiting frequency
•
Low CPU overhead and interrupt load
•
Efficient data transfer to or from the CPU memory with dedicated High-End-Timer Transfer Unit (HTU)
or DMA
•
Diagnostic capabilities with different loopback mechanisms and pin status readback functionality
5.4.2
N2HET RAM Organization
The timer RAM uses 4 RAM banks, where each bank has two port access capability. This means that one
RAM address may be written while another address is read. The RAM words are 96-bits wide, which are
split into three 32-bit fields (program, control, and data).
5.4.3
Input Timing Specifications
The N2HET instructions PCNT and WCAP impose some timing constraints on the input signals.
1
NHETx
3
4
2
Figure 5-5. N2HET Input Capture Timings
Copyright
©
2011, Texas Instruments Incorporated
Peripheral Information and Electrical Specifications
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