UM10462 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2016. All rights reserved.
User manual Rev. 5.5 — 21 December 2016 498 of 523
NXP Semiconductors
UM10462
Chapter 24: LPC11U3x/2x/1x Appendix ARM Cortex-M0
If calibration information is not known, calculate the calibration value required from the
frequency of the processor clock or external clock.
24.5.4.5 SysTick usage hints and tips
The interrupt controller clock updates the SysTick counter.
Ensure software uses word accesses to access the SysTick registers.
If the SysTick counter reload and current value are undefined at reset, the correct
initialization sequence for the SysTick counter is:
1. Program reload value.
2. Clear current value.
3. Program Control and Status register.
24.6 Cortex-M0 instruction summary
Table 455. SYST_CALIB register bit assignments
Bits Name Function
[31] NOREF Reads as one. Indicates that no separate reference clock is provided.
[30] SKEW Reads as one. Calibration value for the 10ms inexact timing is not known
because TENMS is not known. This can affect the suitability of SysTick
as a software real time clock.
[29:24] - Reserved.
[23:0] TENMS Reads as zero. Indicates calibration value is not known.
Table 456. Cortex M0- instruction summary
Operation Description Assembler Cycles
Move 8-bit immediate MOVS Rd, #<imm> 1
Lo to Lo MOVS Rd, Rm 1
Any to Any MOV Rd, Rm 1
Any to PC MOV PC, Rm 3
Add 3-bit immediate ADDS Rd, Rn, #<imm> 1
All registers Lo ADDS Rd, Rn, Rm 1
Any to Any ADD Rd, Rd, Rm 1
Any to PC ADD PC, PC, Rm 3
Add 8-bit immediate ADDS Rd, Rd, #<imm> 1
With carry ADCS Rd, Rd, Rm 1
Immediate to SP ADD SP, SP, #<imm> 1
Form address from SP ADD Rd, SP, #<imm> 1
Form address from PC ADR Rd, <label> 1
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