Advanced Embedded Systems

☛ Ultraviolet EPROM is used in the version 8751.

☛ Here it becomes easier to erase the data using uv rays.

☛ It takes around 20 minutes to erase the data.

☛ To overcome this short coming flash ROM versions of 8751 available.

Timers in embedded system are used in multiple ways

☛ Real Time Clock (RTC) for the system

☛ Initiating an event after a preset time delay

☛ Initiating an even after a comparison of preset times

☛ Capturing the count value in timer on an event

☛ Between two events finding the time interval

☛ Time slicing for various tasks

☛ Time division multiplexing

☛ Scheduling of various tasks in RTOS

☛ It is a command used to jump if no carry occurs after an arithematic operation.

☛ It is called as jump if no carry( conditional jump instruction).

☛ Here the carry flag bit in PSW register is used to make decision.

☛ The processor looks at the carry flag to see if it is raised or not.

☛ If carry flag is 0 ,CPU fetches instructions from the address of the label.

☛ Label name should be unique and must contain alphabetic letters in both uppercase and lowercase.

☛ 1st letter should always be an alphabetic letter.

☛ It can also use digits and special characters ?,.,@,_,$.

☛ Label should not be one of the reserved words in assembly language.

☛ These labels make the program much easier to read and maintain.

☛ EQU is the equate assmbler directive used to define a constant without occupying a memory location.

☛ It associates a constant value with data label .

☛ Whenever the label appears in the program ,constant value is subsituted for label.

☛ Advantage: The constant value occuring at various positions in a program can be changed at once using this directive.

☛ Syntax: label EQU constant value

☛ This file is also called as list file.

☛ It lists the opcodes ,addresses and errors detected by the assembler.

☛ List file is produced only when indicated by the user.

☛ It can be accessed by an editor and displayedon monitor screen or printed.

☛ Progammer uses this file to find the syntax errors and later fix them.

Real-time embedded systems are computer systems that monitor, respond or control an external environment. This environment is connected to the computer system through actuators, sensors, and other input-output interfaces.

For embedded system, the buses used for communication includes

I2C: It is used for communication between multiple ICs

CAN: It is used in automobiles with centrally controlled network

USB: It is used for communication between CPU and devices like mouse, etc.

While ISA, EISA, PCI are standard buses for parallel communication used in PCs, computer network devices, etc.

Model transformations involve multiple models that are used to define different views of a system. It provides different level of granularity that it doesn’t use either the top-down approach or the bottom-up approach to implement the basic functionality of the system. It is used to integrate the library components used that involves the iteration of the model that needs to be constructed. It also involves the analysis of the model so that the process can be made automated by using the construction tools. The compilation made the progress by improving the code that is written in high level language and the code generator produce the code that is required for the machine language.

☛ Atmel Corporation is manufacturing flash ROM

☛ At 89C51 chip of atmel is using flash ROM.

☛ Here no Rom eraser is needed.

☛ Erasing process is done by the PROM burner itself.

☛ To avoid use of PROM burner the 8052 version support in-system programming.

☛ The flag register also called as the program status word uses only 6 bits.

☛ The two unused bits are user defineable flags.

☛ Carry, auxillary carry, parity and overflow flags are the conditional flags used in it.

☛ PSW.1 is a user definable bit and PSW.5 can be used as general purpose bit.

☛ Rest all flags indicate some or the other condition of an arithmetic operation.

☛ Port0 and port2 together form the 16 bit address for external memory.

☛ Port0 uses pins 32 to 39 of 8051 to give the lower address bits(AD0-AD7)

☛ Port2 uses pins 21 to 28 of 8051 to give the higher address bits(A8-A15)

☛ This 16 bit address is used to access external memory if attached.

☛ When connected to external memory they cannot be used as input output ports.

☛ Damage of memory devices due to transient current and static discharges.

☛ Malfunctioning of address lines due to a short in the circuit.

☛ Malfunctioning of Data lines.

☛ Some memory locations being inaccessible in storage due to garbage or errors.

☛ Improper insertion of Memory devices into the memory slots.

☛ Faulty control signals.

Interrupt latency is a time taken to return from the interrupt service routine post handling a specific interrupt. By writing minor ISR routines, interrupt latency can be reduced.

Microprocessor is managers of the resources (I/O, memory) which lie outside of its architecture

Microcontroller have I/O, memory, etc. built into it and specifically designed for control