STM32F100x4, STM32F100x6, STM32F100x8, STM32F100xB
Description
2.6
Nested vectored interrupt controller (NVIC)
The STM32F100xx value line embeds a nested vectored interrupt controller able to handle
up to 41 maskable interrupt channels (not including the 16 interrupt lines of Cortex™-M3)
and 16 priority levels.
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Closely coupled NVIC gives low latency interrupt processing
Interrupt entry vector table address passed directly to the core
Closely coupled NVIC core interface
Allows early processing of interrupts
Processing of late arriving higher priority interrupts
Support for tail-chaining
Processor state automatically saved
Interrupt entry restored on interrupt exit with no instruction overhead
This hardware block provides flexible interrupt management features with minimal interrupt
latency.
2.7
2.8
External interrupt/event controller (EXTI)
The external interrupt/event controller consists of 18 edge detector lines used to generate
interrupt/event requests. Each line can be independently configured to select the trigger
event (rising edge, falling edge, both) and can be masked independently. A pending register
maintains the status of the interrupt requests. The EXTI can detect an external line with a
pulse width shorter than the Internal APB2 clock period. Up to 80 GPIOs can be connected
to the 16 external interrupt lines.
Clocks and startup
System clock selection is performed on startup, however the internal RC 8 MHz oscillator is
selected as default CPU clock on reset. An external 4-24 MHz clock can be selected, in
which case it is monitored for failure. If failure is detected, the system automatically switches
back to the internal RC oscillator. A software interrupt is generated if enabled. Similarly, full
interrupt management of the PLL clock entry is available when necessary (for example on
failure of an indirectly used external crystal, resonator or oscillator).
Several prescalers allow the configuration of the AHB frequency, the high-speed APB
(APB2) and the low-speed APB (APB1) domains. The maximum frequency of the AHB and
the APB domains is 24 MHz.
2.9
Boot modes
At startup, boot pins are used to select one of three boot options:
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Boot from user Flash
Boot from system memory
Boot from embedded SRAM
The boot loader is located in System Memory. It is used to reprogram the Flash memory by
using USART1. For further details please refer to AN2606.
Doc ID 16455 Rev 2
15/84
STMICROELECTRONICS [ ST ]
