difference between max485 and sn75176?

[abbas1707]

max485 circuit

hi guys,

is there any difference between these two ic's functionality??

Regards

 

[vsmGuy]

sn75176 max485

yes !

More answers : GIVEN CLEARLY IN the datasheet !

In fact, I would go on to say sn75176 is best of Rs 422 and max485 for RS 485

 

[laktronics]

sn75176 circuit

Hi,
They can be used interchangeably with each other.
Regards,
Laktronics

 

[abbas1707]

sn75176 application

thanks a lot

i made a circuit for communication between microcontrollers..1 master / multiple slaves and full duplex. please can you guys have a look on it , and tell me where i made mistakes. i know im missing some resistors also but really dnt know about them.so please guide me

thanx

 

[FvM]

max485 sn75176

The circuit is basically OK. Dependending on cable length you should have 120 ohms parallel (A to B) termination at the receiver. The Slave to Master channel, that hasn't a transmitter enabled permanently, should have weak pullup/-down resistors to set the line level to defined idle state (A to VCC, B to GND). Additionally, you may use a combined full-duplex receiver/transmitter chip, e. g. TI SN65HVD3083E instead of two MAX485 or similar.

Regarding the original topic question, there are mainly differencs in speed and power consumption. My standard chip is SN75LBC176, that is fast (10 MBps) and also low power. Standard SN75176 has unpleasant high idle supply current, but is very cheap.

 

[abbas1707]

sn75176

thanx a lot

what about this one??

regards

 

[laktronics]

max485 application

Hi,
1.You can keep RE- permanently grounded and use logic control only for transmission on slave side. On the Master side, you can permanently enable both the transmitter and the receiver.
2. For such 4-wire applications, you can also use MAX 488 to MAX 491 ICS depending up on your application and cost considerations.

Regards,
Laktronics

 

[vsmGuy]

sn75176 full duplex

Abbas !

The circuits are becoming better !

But you have not told us if you want to use the ICs for long distance only or for multipoint communications too..

If so, how many points ?

If I helped you, do click on helped me button

 

[abbas1707]

circuit full-duplex max485

long distance( about 100 meters) + multipoint.
yes i have to do for atleast 10 nodes.

Anyway thanks for reply

 

[vsmGuy]

what are different max485 sn75176

100 Meters and around 20 nodes is not issue for the ultra cheap SN75175.

Termination is of the utmost importance.. RS422.485 is really hard to get correct by people who have not done it before.

However, a good protocol is equally important .. try SMBus !

If I helped you, do click on helped me button

 

[abbas1707]

sn75176 and db9 application circuit

thank you vsmGuy for guidance!

what about termination resistance my last circuit?? actually im not getting the termination concept...can you tell me where i have to place them in last circuit?
really im confused about termination

and about protocol..... can i implement CAN here... i.e using physical layer of rs485 ?

Regards

 

[FvM]

max485 application circuit

With fullduplex (one-way transmission with transmitter always enabled), you need a termination resistor at the receiver-side line end. That also implies,you shouldn't have long stubs connected to the line, if multiple receivers are connected, the line should pass each receiver without a stub, if possible. Full duplex line must be terminated at both ends.

CAN uses a driver hardware different from RS485, although it also works on differential pair.

 

[abbas1707]

max485 resistor

thank you FvM
can you tell me...as i have described my application
which one protocol will be better for my application..
SMBus,CAN or any other

 

[FvM]

sn75176 application note

I don't know, how SMBus should be implemented on RS485, it isn't UART based at all. Protocol should follow on your communication requirements, but I didn't hear about this point except for the multipoint aspect. So device adressing is apparently necessary. Additionally, you may either have a data addressing for the nodes or you can use free formatted telegrams. If data addressing is suitable, MODBUS could be a simple protocol, that would allow to access single and multiple registers and bits. Also the device addressing is defined.

 

[abbas1707]

max485 termination resistance

thank u u Fvm....
im thinking to go with CAN, i know something like this
master>CAN controller>CAN transceiver>----- CAN bus-----

is that right configuration? also when doing CAN is it better to implement CAN protocol in software
or making use of CAN stand alone controller?

please guide me!!
btw i implemented a very simple protocol for 1 master 3 slaves and its working in full duplex
but need is to implement some standard protocol.

Regards!

 

[FvM]

sn75176 application notes

Can needs a special controller cause the frame is partly different from regular UART. µP with on chip CAN controller should work.

 

[tension885]

sn75176 communication

hello ,
i want to implement modbus protocol over rs485 layer in full duplex mode. i have at89c51 microcontroller as master and it has 25 slaves(at89c51). i have read modbus specification manual.and i wish to implement Modbus ASCII.
i dont wana implement all functions. i want to go with following functions
1>read coil status
2> read input status
3> read holding registers
4> Read Input Registers
5> Force Single Coil
6>Preset Single Register

i just need some sample code in c language.or some sample algorithm as reference. or if anyone who have implemented modebus please guide me.
i just need starting point and some programming guideline.
so please help me doing this!!
any help will be appreciated!

Thankx in advance...
Looking for some response

Added after 57 minutes:

please help frends...i know lot of people on this forum have worked on Modbus

 

[engineer.amir@hotmail.com]

Hi

you can get all necessary information for implementing modbus protocol from The Modbus Organization. CCS has made drivers for modbus protocol and it would be benificial for you to study the provided driver file before implementing your own.

I have implemented the modbus protocol and working properly but that is for PIC microcontroller using CCS C compiler and for AT89C51 you may be using uVision Keil IDE therefore study the protocole in detail and then implement it.

Regard
Amir Rashid

 

[xxtigerxx]

i think for me the value for money IC is SN65NVD3082 from texas.
MAX 485 has problem with ESD and long cables installation with big noise.
SN75176 is vey old IC.

 

[nikhilele]

its IC is SN65HVD3082 from texas