Sharing LTC1298

Guido

Is this possible. I am running out of I/O for this project and I am hoping that I can share Inputs to a LTC1298. I am attempting to use two LTC1298 for input for a setpoint. They will be working independently of each other until setpoint is reached. Ok, Is the following feaseable or back to a 40 pin stamp.

CS········· PIN· 0····························· · ' A/D CHIP SELECT
CLK········ PIN· 1····························· · ' A/D CLOCK
*DIO_N0····· PIN· 2··························· ' A/D DATA I/O

CS1········ PIN· 0····························· · ' A/D CHIP SELECT
CLK1······· PIN· 1····························· · ' A/D CLOCK
*DIO_N1····· PIN· 3··························· ·' A/D DATA I/O

As You can see I will not be using the same Data I/O....

Thanks
Guido

Chris Savage

Guido,

·· On SPI devices it's the Data and Clock lines you do want to share.· The CS lines are what need to be separate.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com

Guido

Chris,
Thank You very much, If I am understanding you then this should do the Trick.

CS PIN 3 ' A/D CHIP SELECT
CLK PIN 1 ' A/D CLOCK
DIO_N0 PIN 2 ' A/D DATA I/O

CS1 PIN 4 ' A/D CHIP SELECT
CLK1 PIN 1 ' A/D CLOCK
DIO_N1 PIN 2 ' A/D DATA I/O

Chris Savage

Correct, SPI devices can share the same clock and data lines, but should have separate CS lines.· If the chip is bi-directional, a 1K resistor between it's data line and the stamp pin will prevent damage to the pins should two be in an output state somehow.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com