we have designed a new board that has to read 48 digital inputs. The board is 24V power supply, also inputs can be 0V or 24V.
We connected 6 devices SN65HVS882PWPRG4 together using SPI interface in chain mode.
All works well when inputs are different from "11111111", but when all 8 digital inputs are at logic high the device reads 0.
When 7 digital inputs are at logic 1 and one of them is at logic 0 the SPI reads good values and the same for all the combinations, except 11111111.
This happens for each of the 6 devices.
Current consumption at each input is limited setting current limiting resistance, we tried with 3mA and also 1.5mA but behaviour is the same. What I noticed is that connecting one input at time at 24V and measuring input current, the current increases a little bit more connecting the last 4 inputs and it reaches a maximum value when 7 inputs are high, the last input makes the current to decrease a little bit and SPI reads 0.