LPC1113FHN33/303,5 NXP Semiconductors, LPC1113FHN33/303,5 Datasheet - Page 399

• Manufacturer Part Number: LPC1113FHN33/303,5
• Description: ARM Microcontrollers - MCU Cortex-M0 24 kB flash up to 8kB SRAM
• Manufacturer: NXP Semiconductors

Specifications of LPC1113FHN33/303,5

• Rohs: yes
• Core: ARM Cortex M0
• Processor Series: LPC1113
• Data Bus Width: 32 bit
• Maximum Clock Frequency: 50 MHz
• Program Memory Size: 24 KB
• Data Ram Size: 4 KB
• On-chip Adc: Yes
• Operating Supply Voltage: 1.8 V to 3.6 V
• Operating Temperature Range: - 65 C to + 150 C
• Package / Case: HVQFN-33
• Mounting Style: SMD/SMT
• Factory Pack Quantity: 260

NXP Semiconductors
24.6 Functional description
24.7 Example timer calculations
UM10398
User manual
24.5.4 System Timer Calibration value register (SYST_CALIB - 0xE000 E01C)
The value of the SYST_CALIB register is driven by the value of the SYSTCKCAL register
in the system configuration block (see
Table 360. System Timer Calibration value register (SYST_CALIB - 0xE000 E01C) bit
The SysTick timer is a 24-bit timer that counts down to zero and generates an interrupt.
The intent is to provide a fixed 10 millisecond time interval between interrupts. The
SysTick timer is clocked from the CPU clock (the system clock, see
reference clock, which is fixed to half the frequency of the CPU clock. In order to generate
recurring interrupts at a specific interval, the SYST_RVR register must be initialized with
the correct value for the desired interval. A default value is provided in the SYST_CALIB
register and may be changed by software. The default value gives a 10 millisecond
interrupt rate if the CPU clock is set to 50 MHz.
The following example illustrates selecting the SysTick timer reload value to obtain a
10 ms time interval with the LPC111x/LPC11Cxx system clock set to 50 MHz.
Example (system clock = 50 MHz)
The system tick clock = system clock = 50 MHz. Bit CLKSOURCE in the SYST_CSR
register set to 1 (system clock).
RELOAD = (system tick clock frequency  10 ms) 1 = (50 MHz  10 ms) 1 = 5000001
= 499999 = 0x0007A11F.
Bit
23:0
29:24
30
31
To use the system tick timer, do the following:
1. Program the SYST_RVR register with the reload value RELOAD to obtain the desired
2. Clear the SYST_CVR register by writing to it. This ensures that the timer will count
3. Program the SYST_SCR register with the value 0x7 which enables the SysTick timer
time interval.
from the SYST_RVR value rather than an arbitrary value when the timer is enabled.
and the SysTick timer interrupt.
Symbol
TENMS
-
SKEW
NOREF
description
All information provided in this document is subject to legal disclaimers.
Value
Rev. 12 — 24 September 2012
Chapter 24: LPC111x/LPC11Cxx System tick timer (SysTick)
Description
See
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
See
See
Table
Table
Table
461.
461.
461.
Table
34).
Figure
UM10398
© NXP B.V. 2012. All rights reserved.
8) or from the
Reset
value
0x4
NA
0
0
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