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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
122 of 313
NXP Semiconductors
UM10601
Chapter 10: LPC800 State Configurable Timer (SCT)
10.6.8 SCT state register
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.
Software can read the state associated with a counter at any time. Writing the state is only
allowed when the counter HALT bit is 1; when HALT is 0, a write attempt does not change
the state and results in a bus error.
The state variable is the main feature that distinguishes the SCT 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
•
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.
Table 114. SCT counter register (COUNT, address 0x5000 4040) bit description
Bit
Symbol
Description
Reset
value
15:0
CTR_L
When UNIFY = 0, read or write the 16-bit L counter value. When
UNIFY = 1, read or write the lower 16 bits of the 32-bit unified
counter.
0
31:16
CTR_H
When UNIFY = 0, read or write the 16-bit H counter value. When
UNIFY = 1, read or write the upper 16 bits of the 32-bit unified
counter.
0
Table 115. 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.