STCOM datasheet(17/58 Pages) STMICROELECTRONICS

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STCOM

Description

1.3.8

Multi-AHB bus matrix

The 32-bit multi-AHB bus matrix interconnects all the masters (Cortex™-M4, DMA, and real-

time engine) and the slaves (Flash memory, RAM, AHB and APB peripherals, and real-time

engine) and ensures a seamless and efficient operation even when several high-speed

peripherals work simultaneously.

1.3.9

Timers and watchdog

The STCOM embeds 8 general purpose timers, two advanced timers and one window

watchdog. The Cortex™-M4 is also equipped with a SysTick timer.

General purpose timer (GPT)

The STCOM device includes 8 full-featured general purpose timers based on a 16-bit

autoreload up/down counter and a 16-bit programmable prescaler.

Advanced timers (AT)

The STCOM includes 2 advanced-control timers based on a 16-bit autoreload up/down

counter driven by a 16-bit programmable prescaler. They all feature 4 independent channels

for input capture, output compare, PWM generation or one pulse mode output.

It may be used for a variety of purposes, including measuring the pulse lengths of input

signals (input capture) or generating output waveforms (output compare, PWM,

complementary PWM with deadtime insertion).

Window watchdog (WWDG)

The window watchdog is used to detect the occurrence of a software fault, usually

generated by external interference or by unforeseen logical conditions, which causes the

application program to abandon its normal sequence. The watchdog circuit generates

a device reset on expiry of a programmed time period, unless the program refreshes the

contents of the down counter register. A device reset is also generated if the down counter

value is refreshed before the down counter has reached the proper window register value.

This implies that the counter must be refreshed in a limited window.

The window watchdog is based on a 7-bit free-running down counter with two conditional

resets: the down counter is reloaded outside the window or the down counter value

becomes less than 0x40.

The window watchdog supports early wake-up interrupt trigged when the down counter is

equal to 0x40.

SysTick timer

The Cortex™-M4 has a 24-bit system timer, SysTick, which counts down from the

programmable reload value to zero. It supports the autoreload and can generate

a maskable system interrupt when the counter reaches zero.

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