What is the general use case or purpose of a 3 state tranceiver such as the 74LVT16245?
l
To interface to 16 bit wide devices on a bus.
AWOL, thanks. What do you mean by "interfacing"? Or, to really expose my stupidity... why not just connect BUS A directly with BUS B without a transceiver? Does this IC convert voltage levels? Or is it just meant to more accurately control timing by using a ON/OFF latch on the transceiver?
thanks
The third state (high impedance) effectively makes the device invisible on the bus, so that when the device behind the driver isn't addressed, it can't put its data on to the bus.
If you've only got two devices on the bus, then it probably isn't necessary, except, perhaps for extra drive capability.
Tri-state is usually controlled by a signal called "Output Enable" or "OE", often inverted, so "/OE".
So provided i understand correctly, in other words:
This would risk collisions (in the network sense) on the bus:
(device_a) ---\
-> (device_c)
(device_b) ---/
This would not?
(device_a) ---\
(tristate input bus A)
/OE--( tristate ) -> (device_c)
(tristate input bus B)
(device_b) ---/
whereby the /OE line determines which BUS is output to device_c?
I feel I'm getting closer to understanding this. Thank you for your patience AWOL and please by all means tell me to RTFM and give me some key words I can http://lmgtfy.com when you loose patience.
OR, is it rather this configuration:
(device_a) ---\
(tristate input bus A)
/OE--(tristate outpt bus B) --> (device_c)
(device_b) ------------------------/
In this case /OE is used only to turn off or on device_c access to device_a. device_b assumes it always has access. It's the job of whomever controls /OE to be certain they do not turn on access when device_b is using the bus?
Yes, that's pretty much it.
Address decoding would look at the address bus lines and control the OE pins on the two devices, by uniquely decoding combinations of address values.
For simple schemes that align with power-of-two, the address lines themselves can be used as OE controls.