OM13008,598 NXP Semiconductors, OM13008,598 Datasheet - Page 421

• Manufacturer Part Number: OM13008,598
• Description: BOARD LPC XPRESSO LPC122X
• Manufacturer: NXP Semiconductors
• Series: LPCXpressor

Specifications of OM13008,598

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-6642; OM13008

NXP Semiconductors
UM10441
User manual
25.5.4.2.1 Calculating the RELOAD value
25.5.4.2 SysTick Reload Value Register
25.5.4.3 SysTick Current Value Register
25.5.4.4 SysTick Calibration Value Register
Table 392. SYST_CSR bit assignments
The SYST_RVR specifies the start value to load into the SYST_CVR. See the register
summary in
Table 393. SYST_RVR bit assignments
The RELOAD value can be any value in the range 0x00000001-0x00FFFFFF. You can
program a value of 0, but this has no effect because the SysTick exception request and
COUNTFLAG are activated when counting from 1 to 0.
To generate a multi-shot timer with a period of N processor clock cycles, use a RELOAD
value of N-1. For example, if the SysTick interrupt is required every 100 clock pulses, set
RELOAD to 99.
The SYST_CVR contains the current value of the SysTick counter. See the register
summary in
Table 394. SYST_CVR bit assignments
The SYST_CALIB register indicates the SysTick calibration properties. See the register
summary in
Bits
[2]
[1]
[0]
Bits
[31:24]
[23:0]
Bits
[31:24]
[23:0]
Name
CLKSOURCE
TICKINT
ENABLE
Name
-
CURRENT
Table 25–391
Table 25–391
Table 25–391
Name
-
RELOAD
All information provided in this document is subject to legal disclaimers.
Rev. 1.1 — 10 March 2011
Function
Reserved.
Value to load into the SYST_CVR when the counter is enabled and
when it reaches 0, see
for its attributes. The bit assignments are:
for its attributes. The bit assignments are:
for its attributes. The bit assignments are:
Function
Selects the SysTick timer clock source:
0 = external reference clock
1 = processor clock.
Enables SysTick exception request:
0 = counting down to zero does not assert the SysTick exception
request
1 = counting down to zero to asserts the SysTick exception request.
Enables the counter:
0 = counter disabled
1 = counter enabled.
Function
Reserved.
Reads return the current value of the SysTick counter.
A write of any value clears the field to 0, and also clears the
SYST_CSR.COUNTFLAG bit to 0.
Chapter 25: LPC122x Appendix ARM Cortex-M0
Section
25.5.4.2.1.
UM10441
© NXP B.V. 2011. All rights reserved.
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