ARM PROCESSOR

The ARM processor is widely used in cell phones and many other systems.
INTRODUCTION:
 complex instruction set computers (CISC).
These machines provided a variety of instructions that may perform very complex tasks, such as string searching; they also generally used a number of different instruction formats of varying lengths.
 Reduced instruction set computers (RISC)
These computers tended to provide somewhat fewer and simpler instructions it.
 Streaming data.
Data sets that arrive continuously and periodically are called Streaming data.
 Assembly language:
Assembly language has the following features:
 One instruction appears per line.
 Labels, which give names to memory locations, start in the first column.
 Instructions must start in the second column or after to distinguish them from
 labels.
 Comments run from some designated comment character (; in the case of ARM) to the end of the line
Assemblers must also provide some pseudo-ops to help programmers create complete assembly language programs.An example of a pseudo-op is one that allows data values to be loaded into memory locations.These allow constants,for example, to be set into memory. TheARM % pseudo-op allocates a block of memory of the size specified by the operand and initializes locations to zero.
e.g)
label1 ADR r4,c
LDR r0,[r4] ; a comment
ADR r4,d
LDR r1,[r4]
SUB r0,r0,r1 ; another comment

external interface of the Standard 8051

 Small 8051
Low-cost members of the 8051 family with reduced number of port pins, and no support for off-chip memory. Typical application: Low-cost consumer goods.
 Standard 8051: The Small 8051s and the Extended 8051s are derived
 Extended 8051:Members of the 8051 family with extended range of no-chip facilities (e.g. CAN controllers, ADC, DAC,etc), large numbers of port pins, and - in recent devices - support for large amounts of off-chip memory. Typical applications: Industrial and automotive systems.
Clock frequency and performance
All digital computer systems are driven by some form of oscillator circuit: the 8051 is certainly
no exception. If the oscillator fails, the system will not function at all; if the oscillator runs
irregularly, any timing calculations performed by the system will be inaccurate.

8051 MICROCONTROLLER

8051 is an excellent device for building many embedded systems. One important factor is that the 8051 requires a minimum number of external components in order to operate.

It is a well-tested design; introduced in its original form by Intel in 1980 the development costs of this device now start at less than US $1.00. At this price, you get a performance of around 1 million instructions per second, and 256 bytes (not megabytes!) of on-chip RAM, 32 port pins and a serial interface. Features of 8051: The main features of 8051 microcontroller are:  RAM – 128 Bytes (Data memory)  ROM – 4Kbytes .  Serial Port – Using UART makes it simpler to interface for serial communication.  Two 16 bit Timer/ Counter, Input/output Pins – 4 Ports of 8 bits each on a single chip.  6 Interrupt Sources  8 – bit ALU (Arithmetic Logic Unit)Harvard Memory Architecture – It has 16 bit Address bus (each of RAM and ROM) and 8 bit Data Bus.  8051 can execute 1 million one-cycle instructions per second with a clock frequency of 12MHz. This microcontroller is also called as “System on a chip” because it has all the features on a single chip. The Block Diagram of 8051 Microcontroller is as shown in Figure

Pin configuration of 8051

The following is the Pin diagram of 8051 microcontroller.

PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller’s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.) PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only connect a crystal at these pins to provide clock pulses to the circuit. PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V 500mA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 8051 which runs on +3V. PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If external memory is connected then PIN 31, also called EA/VPP, should be connected to ground to indicate the presence of external memory. PIN 30 is called ALE (address latch enable), which is used when multiple memory chips are connected to the controller and only one of them needs to be selected. PIN 29 is called PSEN. This is "program store enable". In order to use the external memory it is required to provide the low voltage (0) on both PSEN and EA pins.

Embedded computing Unit 1

https://drive.google.com/file/d/0BzsuAfabSI9rX1FhcjBQc1pSMGM/edit?usp=sharing