Level Shifters

19th December 2021 at 7:49pm

https://twitter.com/brouhaha/status/1472718626130206731

Yes. All floppy signals are OC at the driver with pullups at the receiver. The pullups were originally 150 ohm to +5V, hence the need for 40mA drivers (typically SN7438).

On-chip pullups are often current sources rather than resistors, and for not very much current.