UM10462
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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