Thank you for your help. It is tough to know which specs are relevant but I think you've cleared up the issue. A colleague told me that they needed to be TTL inputs but he must have been mistaken.
I’m trying to find an rs485 transceiver with an input type of TTL but it doesn’t seem that any of the datasheets explicitly say they are TTL. Are there any other keywords that will identify the part as such? For datasheets that do have a partial schematic of the chip internals, the topologies do...