Datasheet

STM32F100x4, STM32F100x6, STM32F100x8, STM32F100xB Description
Doc ID 16455 Rev 7 17/88
Each channel is connected to dedicated hardware DMA requests, with support for software
trigger on each channel. Configuration is made by software and transfer sizes between
source and destination are independent.
The DMA can be used with the main peripherals: SPI, DAC, I
2
C, USART, all timers and
ADC.
2.2.14 RTC (real-time clock) and backup registers
The RTC and the backup registers are supplied through a switch that takes power either on
V
DD
supply when present or through the V
BAT
pin. The backup registers are ten 16-bit
registers used to store 20 bytes of user application data when V
DD
power is not present.
The real-time clock provides a set of continuously running counters which can be used with
suitable software to provide a clock calendar function, and provides an alarm interrupt and a
periodic interrupt. It is clocked by a 32.768 kHz external crystal, resonator or oscillator, the
internal low power RC oscillator or the high-speed external clock divided by 128. The
internal low power RC has a typical frequency of 40 kHz. The RTC can be calibrated using
an external 512 Hz output to compensate for any natural crystal deviation. The RTC
features a 32-bit programmable counter for long term measurement using the Compare
register to generate an alarm. A 20-bit prescaler is used for the time base clock and is by
default configured to generate a time base of 1 second from a clock at 32.768 kHz.
2.2.15 Timers and watchdogs
The STM32F100xx devices include an advanced-control timer, six general-purpose timers,
two basic timers and two watchdog timers.
Tabl e 3 compares the features of the advanced-control, general-purpose and basic timers.
Table 3. Timer feature comparison
Timer
Counter
resolution
Counter
type
Prescaler
factor
DMA request
generation
Capture/compare
channels
Complementary
outputs
TIM1 16-bit
Up,
down,
up/down
Any integer
between 1
and 65536
Ye s 4 Ye s
TIM2,
TIM3,
TIM4
16-bit
Up,
down,
up/down
Any integer
between 1
and 65536
Ye s 4 N o
TIM15 16-bit Up
Any integer
between 1
and 65536
Ye s 2 Ye s
TIM16,
TIM17
16-bit Up
Any integer
between 1
and 65536
Ye s 1 Ye s
TIM6,
TIM7
16-bit Up
Any integer
between 1
and 65536
Ye s 0 N o