Data Sheet

Page 32
nRF51822 Product Specification v3.1
4.2 Timer/counters (TIMER)
The timer/counter runs on the high-frequency clock source (HFCLK) and includes a 4 bit (1/2
X
) prescaler that
can divide the HFCLK.
The TIMER will start requesting the 1 MHz mode of the HFCLK for values of the prescaler that gives f
TIMER
less
or equal to 1 MHz. If the timer module is the only one requesting the HFCLK, the system will automatically
switch to using the 1 MHz mode resulting in a decrease in the current consumption. See the parameters
I
1v2XO16,1M
, I
1v2XO32,1M
, I
1v2RC16,1M
in Table 32 on page 47 and I
TIMER0/1/2,1M
in Table 52 on page 61.
The task/event and interrupt features make it possible to use the PPI system for timing and counting tasks
between any system peripheral including any GPIO of the device. The PPI system also enables the TIMER
task/event features to generate periodic output and PWM signals to any GPIO. The number of input/outputs
used at the same time is limited by the number of GPIOTE channels.
Table 12 Timer/counter properties
4.3 Real Time Counter (RTC)
The Real Time Counter (RTC) module provides a generic, low power timer on the low-frequency clock source
(LFCLK). The RTC features a 24 bit COUNTER, 12 bit (1/X) prescaler, capture/compare registers, and a tick
event generator for low power, tickless RTOS implementation.
Table 13 RTC properties
4.4 AES Electronic Codebook Mode Encryption (ECB)
The ECB encryption block supports 128 bit AES block encryption. It can be used for a range of cryptographic
functions like hash generation, digital signatures, and keystream generation for data encryption/decryption.
ECB encryption uses EasyDMA to access system RAM for in-place operations on cleartext and ciphertext
during encryption.
Instance Bit-width Capture/Compare registers
TIMER0 8/16/24/32 4
TIMER1 8/16 4
TIMER2 8/16 4
Instance Capture/Compare registers
RTC0 3
RTC1 4