UM10850
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User manual
Rev. 2.4 — 13 September 2016
184 of 464
NXP Semiconductors
UM10850
Chapter 13: LPC5410x SCTimer/PWM (SCT0)
The state variable is the main feature that distinguishes the SCTimer/PWM from other
counter/timer/ PWM blocks. Events can be made to occur only in certain states. Events, in
turn, can perform the following actions:
•
set and clear outputs
•
limit, stop, and start the counter
•
cause interrupts and DMA requests
•
modify the state variable
The value of a state variable is completely under the control of the application. If an
application does not use states, the value of the state variable remains zero, which is the
default value.
A state variable can be used to track and control multiple cycles of the associated counter
in any desired operational sequence. The state variable is logically associated with a state
machine diagram which represents the SCT configuration. See
and
for more about the relationship between states and events.
The STATELD/STADEV fields in the event control registers of all defined events set all
possible values for the state variable. The change of the state variable during multiple
counter cycles reflects how the associated state machine moves from one state to the
next.
If UNIFY = 1 in the CONFIG register, only the _L bits are used.
If UNIFY = 0 in the CONFIG register, this register can be written to as two registers
STATE_L and STATE_H. Both the L and H registers can be read or written individually or
in a single 32-bit read or write operation.
13.6.10 SCT input register
Software can read the state of the SCT inputs in this read-only register in slightly different
forms.
1. The AIN bit displays the state of the input captured on each rising edge of the SCT
clock This corresponds to a nearly direct read-out of the input but can cause spurious
fluctuations in case of an asynchronous input signal.
2. The SIN bit displays the form of the input as it is used for event detection. This may
include additional stages of synchronization, depending on what is specified for that
input in the INSYNC field in the CONFIG register:
–
If the INSYNC bit is set for the input, the input is triple-synchronized to the SCT
clock resulting in a stable signal that is delayed by three SCT clock cycles.
–
If the INSYNC bit is not set, the SIN bit value is identical to the AIN bit value.
Table 217. SCT state register (STATE, address 0x5000 4044) bit description
Bit
Symbol
Description
Reset value
4:0
STATE_L
State variable.
0
15:5
-
Reserved.
-
20:16
STATE_H
State variable.
0
31:21
-
Reserved.
-