
UM10800
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User manual
Rev. 1.2 — 5 October 2016
293 of 487
NXP Semiconductors
UM10800
Chapter 16: LPC82x SCTimer/PWM
The current state can be read at any time by reading the STATE register.
To change the current state by software (that is independently of any event occurring), set
the HALT bit and write to the STATE register to change the state value. Writing to the
STATE register is only allowed when the counter is halted (the HALT_L and/or HALT_H
bits are set) and no events can occur.
16.7.12 Configure the SCT without using states
The SCT can be used as standard counter/timer with external capture inputs and match
outputs without using the state logic. To operate the SCT without states, configure the
SCT as follows:
•
Write zero to the STATE register (zero is the default).
•
Write zero to the STATELD and STATEV fields in the EVCTRL registers for each
event.
•
Write 0x1 to the EVn_STATE register of each event. Writing 0x1 enables the event.
In effect, the event is allowed to occur in a single state which never changes while the
counter is running.
16.7.13 SCT PWM Example
shows a simple application of the SCT using two sets of match events (EV0/1
and EV3/4) to set/clear SCT output 0. The timer is automatically reset whenever it
reaches the MAT0 match value.
In the initial state 0, match event EV0 sets output 0 to HIGH and match event EV1 clears
output 0. The SCT input 0 is monitored: If input0 is found LOW by the next time the timer
is reset(EV2), the state is changed to state 1, and EV3/4 are enabled, which create the
same output but triggered by different match values. If input 0 is found HIGH by the next
time the timer is reset, the associated event (EV5) causes the state to change back to
state 0where the events EV0 and EV1 are enabled.
The example uses the following SCT configuration:
•
1 input
•
1 output
•
5 match registers
•
6 events and match 0 used with autolimit function
•
2 states