hi everyone, and i hope this finds you all well......

my project is heating up, i am waiting to get the parts (still!!) but i need to work on the thesis and what not.....

i have to write about the rtc and how i am interfacing it with the cpu.......

can anyone comment on this or rather improve on it :p

thanks

eric

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Real Time clock

A real time clock is a dedicated IC that communicates with the microprocessor. It generates time in real-time (hours and minutes), the RTC used in my project is a dallas DS17887 model. The only requirements are an external crystal and a battery source.

There is a 8 bit multiplexed bi-directional bus for communicating with the microcontroller, this serves as both a data and address bus, multiplexed buses save pins on the IC because address and data information share the same signal paths.

Address moves along with ALE (address strobe input- active high) and data moves along with RD and WR lines., the port 0 of the micro would be running open drain so I provided pull-up resistors on port 0 (EA active high)

Likewise the IRQ (interrupt request output) pin on the RTC is also an open drain output so I have a 10k pull up resistor across this, this would prevent any false re-trigger of the 8052 (maybe caused by a noisey environment on board)

In the project I have hooked up the multiplexed bus of the RTC to port 0 of the microcontroller (P0.0 – P0.7)

I don’t need to use the KS(kickstart input- active low) pin of the RTC and have tied it to a high level.



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microprocessors




The microprocessor (central processing unit) is the powerhouse of the system. The microprocessor controls memory and input/output throught a series of buses. The buses select an input/output location or a memory device,transfer data between input/output or memory and the microprocessor, and control the input/output and memory system
Memory and input/output are controlled through instructions that are stored in memory and executed by the microprocessor

The microprocessor performs three basic tasks for the computer system –

I transfer data between cpu-> memory or memory-> input/output

II simple arithmetic and logical operations (for advanced math operations a digital signal processor maybe used)

III program flow via simple decisions, often done on flow diagrams


Through these 3 basic tasks a microprocessor can perform virtually any desired operation.

The power of a microprocessor is determined in MIPS (Million of Instructions Per Second), modern processors such as the Pentium 4 ™ are able to execute in excess of 4 MIPS!.

The speed of a microprocessor is measured in Mega Hertz, or Giga Hertz. The faster the figure, the faster the microprocessor can perform instructions.

The microprocessor evolution started in approx 1971, with the intel 4004, this was a 4 bit device, which could perform a mere 45 instructions, intel then went on to develop a string a microprocessors including the 808x series, which modern hardware is still based upon.

In 1978 they developed the 8086, followed by the 80286. then there was a major breakthrough, as programs, demanding more resources were treated to the worlds first 32 bit microprocessor in the 80386, in the 90’s intel released versions of its successor, the 80486.

In 1993 intel released the Pentium and ditched the 80x86 identification from its microprocessors, instead using the Pentium ™ abbreviation.

The Pentium came in various tastes including the Pentium pro and Pentium II, Pentium 3 and the current model, the Pentium 4, it also was available as the high end xeon type which was typically used for main stream servers or graphic work stations demanding lots of power.

Intel are the worlds largest producer of microprocessors, the other main manufacturer is AMD ™ .

The microprocessor in my project is called a microcontroller, which is basically a mini microprocessor, it is based on intels 8051/8052 family. It is a atmel AT89C55WD, an 8 bit microcontroller.

What this means is that various IC manufacturers develop their own microcontrollers, and nearly all of them are backward compatible with intels own 8051 microcontroller from the 80’s