SN65HVD12: SN65HVD12

Justin Burk

Part Number: SN65HVD12
Other Parts Discussed in Thread: THVD1406

All,

Is it possible to hardwire the SN65HVD12 for Rx and Tx to always be active (DE = 1, RE_N = 0)? The FPGA does not have a spare pin to control remotely. Thanks!

Justin

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 243220 points

In theory, this is possible. But the consequence is that this node always transmits, so no other node on the bus can ever transmit.

If you have an UART(-like) protocol, it might be possible to add logic that pulses DE high for a certain time after any falling edge on D.

0 Justin Burk over 3 years ago in reply to Clemens Ladisch

Prodigy 70 points

Hi Clemens,

0 Justin Burk over 3 years ago in reply to Clemens Ladisch

Prodigy 70 points

Hi Clemens,

0 Justin Burk over 3 years ago in reply to Justin Burk

Prodigy 70 points

For our application, the board with the SN65HVD12 is only transmitting when commanded to do so. The FPGA sends a SPI command to the device of interest to send back whatever information is needed, then the device responds. Is it still true that no other node can transmit? Thanks for your help!

Justin

+1 Hao L over 3 years ago in reply to Justin Burk

TI__Mastermind 25705 points

Justin,

With the device enabled (DE=H), even the device's input (D) is constant (D=H, or D=L) and not toggling, the driver still drives the bus (making A=H/B=L or A=L/B=H). Therefore the other nodes cannot transmit. TI will release a device (THVD1406) with auto directional control feature. You can spare the enable signal.

0 Justin Burk over 3 years ago in reply to Hao L

Prodigy 70 points

Hello Hao and Clemens,

Thank you for your help! I confirmed this is the only Tx node on the bus (there are multiple Rx nodes), so we are good to hardwire DE = 1, RE_N = 0 for the prototype but will keep the new device in mind for future builds.

Justin

0 Clemens Ladisch over 3 years ago in reply to Justin Burk

Guru 243220 points

You said above that the other devices send responses. So you confirmed that that was false?

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SN65HVD12: SN65HVD12