SOFTWARE DEVELOPERs' VIEW oF HaRdwAre (1 Viewer)

[destination]

hey everyone
with the SDVH topic, do we need to know all the data streaming and stuff??
i've learnt and understood gates n alll the convertions....
but what about data streaming devices n all that? cause it covers a big part of the software syllabus for that topic...
thanks

 

[Winston]

Originally posted by destination
hey everyone
with the SDVH topic, do we need to know all the data streaming and stuff??
i've learnt and understood gates n alll the convertions....
but what about data streaming devices n all that? cause it covers a big part of the software syllabus for that topic...
thanks

Yes you need to know about data streaming, about your start bit/stop bit, and the data bits and also the odd parity bit

 

[Fosweb]

Destination: look - don't worry about it. It's actually there for no reason.

 

[Skywalker]

LOL

Just fleshes out the syllabus to make it look intimidating, they won't ask you anything on it...

Seriously speaking, last year's Q on this was writing an algorithm. Don't know how you could have studied for that.

 

[Fosweb]

You can study on how to detect control characters/detecting multiple characters/stop bit detection etc...
Error checking- you can study that bit.

 

[-X-]

How does the "Odd bit parity" error check work? Teacher didn't explain that to us (along with a gazillion other stuff).

 

[Fosweb]

Your data stream will be sent in packets of a set length of bits. You will be told if the stream is using odd or even parity.
This is a way of checking to see if the computer has recieved the packet correctly.
It works like this: (Using ODD parity as an example in an 8 bit packet and a 1 bit parity bit)
The 8 bits are used for data transer, and the other bit is used for parity checking. But before the computer can interpret the data, it needs to make sure that the right data has been sent. If using ODD Parity, then EVERY packet sent must have an ODD number of bits (an odd number of 1's I mean when I say that). So when the packet is recieved, the number of bits are added up to check that there is an odd number of bits). If there isnt an odd number of bits then the packet is returned/rejected whatever you want to call that.
HOW PARITY WORKS:
In odd parity - every packet sent needs to have an odd number of bits. The parity bit is the one that allows for this. If the packet being sent (the 8-bit part of the packet) has an EVEN number of bits, then the parity bit is made 1 to make the total number of bits ODD. If the packet being sent already has an odd number of bits however, the parity bit is made 0, as making it 1 would make there an even number of bits, and thus the packet would be 'bad' packet...

Examples: (8 bits, space, then parity bit) 11100111 1 - Parity bit is 1 here, as there are an even number of 1's in the 8-bit part, and the total number of 1's needs to be ODD for odd parity.
11100110 0 - Parity bit is 0, as there are already an odd number of bits.

HTH.

 

[-X-]

Ok, so basically its counting the 1's and checking to see if it matches what the parity bit says (must be the worst form of error detection i recon )?


Thanks

 

[Fosweb]

Yeah - kindof...
There are some flaws. Namely: what happens if in the transfer of a packet, that packet actually loses TWO (or FOUR or SIX) of the bits it is trying to transfer? The parity bit will not detect any error, because all it is looking for is whether there is an ODD or an EVEN number of bits, which there still will be.

 

[Winston]

i still don't quite understand data packets i read Fosweb's explanation of the odd bit parity, but i'm not quite understanding the concept of the data packet

 

[Winston]

after reading i think i get the odd bit parity concept

so would be right to say that the data packet's bits MUST equate to a sum of an odd number for it to be a good data packet

 

[-X-]

Originally posted by Winston
after reading i think i get the odd bit parity concept

so would be right to say that the data packet's bits MUST equate to a sum of an odd number for it to be a good data packet

The parity bit tells us whether the sum of 1's is even or odd. The reciever will then count the number of 1's and see if it matches what the parity bit is saying (ie even or odd number). If it matches then everything is supposedly fine, else, the packet transmited is corrupt and needs to be re-sent.

 

[Winston]

Originally posted by -X-
The parity bit tells us whether the sum of 1's is even or odd. The reciever will then count the number of 1's and see if it matches what the parity bit is saying (ie even or odd number). If it matches then everything is supposedly fine, else, the packet transmited is corrupt and needs to be re-sent.

so is it safe to say the recieved data packet, will be check to see if the sum of the 1's is a odd, if it is the packet is valid, else the packet is required to be re-sent?

 

[Fosweb]

Yeah. Now you just need to know how this applies to a data stream question, and you'll be set.

 

[Winston]

sounds pretty cool, but im like behind LMAO

do we have to know about all the flip flops variations?

like the RS Flip flop, the NAND and NOR variation,

and for the adders is knowing the half bit and full adder sufficient or do we need to know about the 8 bit adder

 

[-X-]

Originally posted by Winston
so is it safe to say the recieved data packet, will be check to see if the sum of the 1's is a odd, if it is the packet is valid, else the packet is required to be re-sent?

That depends on the type of packet. For example for some packets, Odd = valid while other form of packets say Odd != valid. Thats why there is a parity bit telling the reciever what to accept as being valid. If the parity bit says "0" meaning even, then the sum of ones must be an even number for the reciever to accept the packet. If the parity bit says "1" meaning odd, then the sum of ones must be an odd number for the reciever to accept the packet as being valid.

Thats basically how it knows whether the packet recieved is valid or not.

 

[-X-]

Originally posted by Winston
sounds pretty cool, but im like behind LMAO

do we have to know about all the flip flops variations?

like the RS Flip flop, the NAND and NOR variation,

Im not sure about that too. Do we have to know how to construct the gates or do we just have to know how they work?

 

[Inhuman]

We got taught how to draw one, and I think you just need to be able to follow the logic that makes them work if they show you one of the others