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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
219 of 1441
NXP Semiconductors
UM10503
Chapter 14: LPC43xx/LPC43Sxx Clock Control Unit (CCU)
14.5.3 CCU1/2 branch clock configuration registers
Each generated output clock from the CCU has a configuration register. They all follow the
format as described in
and
On the LPC43xx, all branch clocks are in Run mode after reset. Auto and wake-up
features are disabled.
The clock can be configured to run in the following modes described by the bits RUN,
AUTO, and WAKEUP in the CLK_XXX_CFG registers:
RUN —
The WAKEUP, PD, and AUTO control bits determine the activation of the branch
clock. If register bit AUTO is set, the AHB disable protocol must complete before the clock
is switched off. The PD bit is shown in
.
AUTO —
Enable auto (AHB disable mechanism). The PMU initiates the AHB disable
protocol before switching the clock off. This protocol ensures that all AHB transactions
have been completed before turning the clock off. However, if a bus master initiates a
transfer and the bus is still active, ensure that all transfers have completed before turning
off the master clock in auto mode. Otherwise, data may be lost when the master clock is
turned off and the master can’t process a response from the bus.
WAKEUP —
The branch clock is wake-up enabled under the following conditions:
•
The PD bit in the Power Mode register (see
) is set.
•
Wake-up enabled clocks are switched off.
Wake-up enabled clocks are switched on when a wake-up event is detected or when the
PD bit is cleared. If register bit AUTO is set, the AHB disable protocol must complete
before the clock is switched off.
Remark:
To disable any of the branch clocks safely, use two separate writes to the
CLK_XXX_CFG register: first set the AUTO bit, and then on the next write, disable the
clock by setting the RUN bit to zero.
4
BASE_UART0_
CLK
Base clock indicator for BASE_UART0_CLK
0 = All branch clocks switched off.
1 = At least one branch clock running.
1
R
5
BASE_SSP1_
CLK
Base clock indicator for BASE_SSP1_CLK
0 = All branch clocks switched off.
1 = At least one branch clock running.
1
R
6
BASE_SSP0_
CLK
Base clock indicator for BASE_SSP0_CLK
0 = All branch clocks switched off.
1 = At least one branch clock running.
1
R
7
-
Reserved.
-
-
31:8
-
Reserved.
-
-
Table 162. CCU2 base clock status register (CCU2_BASE_STAT, address 0x4005 2004) bit
description
…continued
Bit
Symbol
Description
Reset
value
Access