UM10850
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User manual
Rev. 2.4 — 13 September 2016
170 of 464
NXP Semiconductors
UM10850
Chapter 13: LPC5410x SCTimer/PWM (SCT0)
driven as well and can therefore happen without software intervention. By defining these
states, the SCTimer/PWM provides the means to run entire state machines in hardware
with any desired level of complexity to accomplish complex waveform and timing tasks.
In a simple system such as a classical timer/counter with capture and match capabilities.
all events that could cause the timer to capture the timer value or toggle a match output
are enabled and remain enabled at all times while the counter is running. In this case, no
events are filtered and the system is described by one state that does not change. This is
the default configuration of the SCT.
In a more complex system, two states could be set up that allow some events in one state
and not in the other. An event itself, enabled in both states, can then be used, to move
from one state to the other and back while filtering out events in either state. In such a
two-state system different waveforms at the SCT output can be created depending on the
event history. Changing between states is event-driven and happens without any
intervention by the CPU.
Formally, the SCTimer/PWM can be programmed as state machine generator. The ability
to perform switching between groups of events provides the SCT the unique capability to
be utilized as a highly complex State Machine engine. Events identify the occurrence of
conditions that warrant state changes and determine the next state to move to. This
provides an extremely powerful control tool - particularly when the SCT inputs and outputs
are connected to other on-chip resources (ADC triggers, other timers etc.) in addition to
general-purpose I/O.
In addition to events and states, the SCTimer/PWM provides other enhanced features:
•
Four alternative clocking modes including a fully asynchronous mode.
•
Selection of any SCT input as a clock source or a clock gate.
•
Capability of selecting a “greater-than-or-equal-to” match condition for the purpose of
event generation.
Fig 20. SCTimer/PWM block diagram
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