gpib controller enquiry(gpib guru)

[tezamm]

hi

i recently had a problem getting control of the atn bit but succeded with your help.
now although i can switch the atn bit by setting the controller in standby mode, i still cannot send data bytes. i found some info that said that i should address the 7210 to itself talk and listen. does that make sense to you? because it sounds strange

if so, any ideas??

thanks again

[GPIB_Guru]

Before you can send data bytes, you must send control bytes to address the bus correctly. Setting the 7210 to talk and listen would not be addressing the bus correctly. A correctly addressed bus has one talker and one or more listeners. Here are the steps required to send a message to a device:
1. Assert Attention
2. Unlisten (0x3F)
3. MLAx, where X is the address of the device (0x20 | DevicePad)
4. MTAy, where Y is the your address (0x40 | ControllerPad)
5. Deasserte Attention
6. Transfer the data bytes

[tezamm]

hi thanks for replying.
yes it make sense. I tried it out it works, but not with a go to standby to deassert the atn bit!
when using gts the atn deasserts but i cannot send data bytes.

it seems to work properly only with disable system control instead of gts and then reassert the ren enamble bit to reassert atn.

does it make sense to you? and do you know whether the disable system control just releases the controller from the it's CIC status only?as if does only that i could use it to deassert atn

thanks again

[GPIB_Guru]

gts should work. It should transition you from an active controller to a standby controller. This deasserts ATN and allows you to transmit data bytes. I know that it works with the NAT7210. You should be able to look at the ADSR to see if the chip thinks it is a talker/listener. This could be a bug in the chip. You may want to contact the manufacturer for more information.

Disabling system control switches the direction of the REN and IFC lines in the transceivers. The side effect is that the REN line will be deasserted and all devices will enter local state.

[tezamm]

hi

yes it makes sense. one thing i noticed is that a gts effects also the nrfd line(deasserts it).this could be the reason why i cannot send data bytes.

i will try some more and i will get back to you if i succeed.

thanks