An embedded system consist of several components.
Special Hardware: cryptographic.hardware.accelerators
Hardware developers often use interfaces that can directly write to chip registers or flash: JTAG, debug ports/pins
Embedded systems are designed and often have drawbacks for their advantages. Low power consumption and low performance (Benchmark: performance/watt comparisons) In contrast to the early age of computers many vendors do not publish data sheets or programming handbooks for their SoC, Wireless Chips, Boards.
see hardware tags