UM10503
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User manual
Rev. 1.3 — 6 July 2012
842 of 1269
NXP Semiconductors
UM10503
Chapter 28: LPC43xx State Configurable Timer (SCT)
28.7.10.1.4
Configure multiple states
1. In the EVSTATEMASK register for each event (up to 16 events, one register per
event), select the state or states (up to 31) in which this event is allowed to occur.
Each state can be selected for more than one event.
2. Determine how the event affects the system state:
In the EVCTRL registers (up to 16 events, one register per event), set the new state
value in the STATEV field for this event. If the event is the highest numbered in the
current state, this value is either added to the existing state value or replaces the
existing state value, depending on the field STATELD.
Remark:
If there are higher numbered events in the current state, this event cannot
change the state.
If the STATEV and STATELD values are set to zero, the state does not change.
28.7.10.1.5
Miscellaneous options
•
There are a certain (selectable) number of capture registers. Each capture register
can be programmed to capture the counter contents when one or more events occur.
•
If the counter is in bidirectional mode, the effect of set and clear of an output can be
made to depend on whether the counter is counting up or down by writing to the
OUTPUTDIRCTRL register.
•
<tbd>
28.7.10.2 Operate the SCT
1. Configure the SCT (see
Section 28.7.10.1 “Configure the SCT”
).
a. Configure the counter (see
).
b. Configure the match and capture registers (see
c. Configure the events and event responses (see
).
d. Configure multiple states (
).
2. Write to the STATE register to define the initial state. By default the initial state is state
0.
3. To start the SCT, write to the CTRL register:
–
Clear the counters.
–
Clear or set the STOP_L and/or STOP_H bits.
Remark:
The counter starts counting once the STOP bit is cleared as well. If the
STOP bit is set, the SCT waits instead for an event to occur that is configured to
start the counter.
–
For each counter, select unidirectional or bidirectional counting mode (field
BIDIR_L and/or BIDIR_H).
–
Select the prescale factor for the counter clock (CTRL register).
–
Clear the HALT_L and/or HALT_H bit. By default, the counters are halted and no
events can occur.
4. To stop the counters by software at any time, stop or halt the counter (write to
STOP_L and/or STOP_H bits or HALT_L and/or HALT_H bits in the CTRL register).