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Understanding ARM7 Microcontroller based embedded hardware

The following figure shows the ARM7 Microcontroller. The large grey color rectangle represents the microcontroller chip. This single chip includes all the components required for the computer hardware. In the case of 8086 kit, every component like CPU, Memory and IO interfaces are present as separate chips. These are interconnected using tracks on the PCB (Printed Circuit Board). In the case of microcontroller, all the components are included in a single chip, and interconnected exactly like in a PCB. So for our understanding, microcontroller is like a PCB and other chips included in a single chip. Microcontroller is also referred as 'System On Chip' (SOC). I feel SOC is more appropriate name for the microcontroller.

The pins coming out of the SOC chip, are IO device interface pins from the IO interface chips present in side the SOC. We place the SOC chip on a PCB. Some IO interface pins are connected to the on board (PCB) IO devices like LEDs, Push buttons, and LCD display. Other IO interface pins are brought to the IO connectors present on the PCB. Typical connectors are RS-232 connector, PS/2 keyboard connector, USB device connector, and SD Card (memory card) socket. Now external IO devices are connected to these connectors by using appropriate cables.

The ARM7 CPU is a 32 bit CPU. It contains 16 registers. All registers are 32 bit in size. All instructions are 32 bit in size. All instructions uses only registers as operands. So it does not support operations directly on the memory operands, as 8086 CPU. So ARM CPU is considered as RISC (Reduced Instruction Set Computer) model CPU and 8086 is considered as CISC (Complex Instruction Set Computer) model CPU. Another important difference is regarding address spaces. 8086 support two separate address spaces, one address space is for memory and other is for IO. Where as ARM has only single address space, which is a combined address space for both memory and IO.

In the ARM SOC shown above, it got 512K of flash ROM, and 32K of static RAM. It has got the following IO interfaces:

  • General Purpose IO (GPIO)
  • Serial communication interface
  • Timer/Counter/Pulse Width Modulator(PWM)
  • Analog to Digital converter (ADC)
  • Digital to Analog converter (DAC)
  • Inter IC communication (I2C) interface
  • Serial Peripheral Interface (SPI)
  • Universal Serial Bus (USB) device interface

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