
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
268 of 487
NXP Semiconductors
UM10800
Chapter 16: LPC82x SCTimer/PWM
16.6.2 SCT configuration register
This register configures the overall operation of the SCT. Write to this register before any
other registers. Only word-writes are permitted to this register. Attempting to write a
half-word value results in a bus error.
Table 223. SCT configuration register (CONFIG, address 0x5000 4000) bit description
Bit
Symbol
Value
Description
Reset
value
0
UNIFY
SCT operation
0
0
The SCT operates as two 16-bit counters named L and H.
1
The SCT operates as a unified 32-bit counter.
2:1
CLKMODE
SCT clock mode
00
0x0
System Clock Mode. The system clock clocks the entire SCT module including
the counter(s) and counter prescalers.
0x1
Sampled System Clock Mode. The system clock clocks the SCT module, but
the counter and prescalers are only enabled to count when the designated
edge is detected on the input selected by the CKSEL field. The minimum pulse
width on the selected clock-gate input is one system clock period. This mode is
the high-performance, sampled-clock mode.
0x2
SCT Input Clock Mode. The input/edge selected by the CKSEL field clocks the
SCT module, including the counters and prescalers, after first being
synchronized to the system clock. The minimum pulse width on the clock input
is 1 bus clock one system clock period. This mode is the low-power,
sampled-clock mode.
0x3
Asynchronous Mode. The entire SCT module is clocked directly by the
input/edge selected by the CKSEL field. In this mode, the SCT outputs are
switched synchronously to the SCT input clock - not the system clock. The input
clock rate must be at least half the system clock rate and can be the same or
faster than the system clock.
6:3
CKSEL
SCT clock select. The specific functionality of the designated input/edge is
dependent on the CLKMODE bit selection in this register.
0000
0x0
Rising edges on input 0.
0x1
Falling edges on input 0.
0x2
Rising edges on input 1.
0x3
Falling edges on input 1.
0x4
Rising edges on input 2.
0x5
Falling edges on input 2.
0x6
Rising edges on input 3.
0x7
Falling edges on input 3.
7
NORELAOD_L
-
A 1 in this bit prevents the lower match registers from being reloaded from their
respective reload registers. Setting this bit eliminates the need to write to the
reload registers MATCHREL if the match values are fixed. Software can write to
set or clear this bit at any time. This bit applies to both the higher and lower
registers when the UNIFY bit is set.
0
8
NORELOAD_H
-
A 1 in this bit prevents the higher match registers from being reloaded from their
respective reload registers. Setting this bit eliminates the need to write to the
reload registers MATCHREL if the match values are fixed. Software can write to
set or clear this bit at any time. This bit is not used when the UNIFY bit is set.
0