MCP23x17 CS line question

[umodjm]

Hi all,
I'm new to the scene. I don't have a whole lot of EE background, but I've been pouring over the datasheet[1] for MCP23S17 now for a couple of days. I'm trying to design a controller using these chips. I have one question though. The /CS line is active high.. and I'm planning on interfacing via the parallel port. I had initially thought I could just tie pin 1 on the parallel port to the /CS line on the MCP.. but now I'm second guessing myself. Should there be a resistor inline also? If i pull pin 1 low, how do I know how much current I'll be sinking and whether or not I'll then be in the market for a new motherboard? Section 2.0 "Absolute maximum ratings" says "maximum output current sourced by any output pin is 25mA" but /CS is not an output, it's an input. Section 2.1 "DC Characteristics" says that the minimum voltage on /CS is Vss and the maximum is '0.8 VDD'" whatever that means...

Please help! I've googled for hours and can't find any info on controlling this chip via parallel port.. everyone is using a PIC and they seem to always tie some pin on the PIC right to /CS on the MCP.


[1] https://www.electro-tech-online.com/custompdfs/2010/01/21952b.pdf

 

[ericgibbs]

Hi all,
I'm new to the scene. I don't have a whole lot of EE background, but I've been pouring over the datasheet[1] for MCP23S17 now for a couple of days. I'm trying to design a controller using these chips. I have one question though. The /CS line is active high.. and I'm planning on interfacing via the parallel port. I had initially thought I could just tie pin 1 on the parallel port to the /CS line on the MCP.. but now I'm second guessing myself. Should there be a resistor inline also? If i pull pin 1 low, how do I know how much current I'll be sinking and whether or not I'll then be in the market for a new motherboard? Section 2.0 "Absolute maximum ratings" says "maximum output current sourced by any output pin is 25mA" but /CS is not an output, it's an input. Section 2.1 "DC Characteristics" says that the minimum voltage on /CS is Vss and the maximum is '0.8 VDD'" whatever that means...

Please help! I've googled for hours and can't find any info on controlling this chip via parallel port.. everyone is using a PIC and they seem to always tie some pin on the PIC right to /CS on the MCP.


[1] https://www.electro-tech-online.com/custompdfs/2010/01/21952b-1.pdf

hi,
The / in front of the CS means that the CS line is active when low. ie: /CS

Do you have the details of the PC parallel port.??

EDIT:
do you plan to control the MCP ic via the PC parallel port.?
Could you explain in more detail why you are interfacing theis MCP.?