Hi,
Sorry for the delay in responding but it has been a bank holiday weekend over here and I have been away.
nobtiba
Hi Rach,
- Then I need to output clock signal from D0 to all MAX7301 ?
- I am not very sure how could I control 4 of them, for example, if I want 112 output logic level 1 then 0; or if I want some pins of the first, second and fourth MAX7301 ouput logic level 1 and the other pins ouput logic level 0 at the same time ?
- Compare to the "decoder solution", using MAX7301 could make "simpler circuit" but is this more expensive and what is the other benefits?
Thank you Rach !
Yes in the solution above you need to output the clock on D0.
Controlling all 4 of them is relatively easy. The port expanders take 16-bit commands sent to them serially. The commands can be sent to control single IO bits or groups of IO bits in each of the expanders. Null commands can also be sent so expanders can be individually accessed without affecting others in the chain.
The MAX7301 makes a simpler circuit and they are relatively inexpensive. I havent worked out the cost for each solution but I suspect there isnt much difference between the two. The other benefit of the port expander is versatility. Maxim website says: "Each port can be configured either as a push-pull logic output capable of sinking 10mA and sourcing 4.5mA, or a Schmitt logic input with optional internal pullup. Seven ports feature configurable transition detection logic, which generates an interrupt upon change of port logic level."
xheavenlyx
#-Link-Snipped-# You seem very familier with PP intefacing. I am working on some related projects at themoment. I am interested on what all you have done till now. It would be nice if you can give a lil article on your experience and the difficulties that has come. Since as it is with any other field, practicle is very different from theory. For example we almost always forget the power requirements and surge protection etc (There was an high impedance IC just for switching which protects the PC Parallel Port, but cant recall the 74HCxx part!?).
Anyway, as for the post I havent used the MAX IC however it seems to be the bast choice here because its specificly used for Port I/O. And moreover, interfacing MUX/DeMUX can get cumber some!, the timing diagrams are not easy.
I've done a little bit with PP interfacing over the years but nothing recently. My main experiences recently are PowerPC processor board design, high speed busses such as DDR, RapidIO, PCI-X and loads of FPGA design.
You are right, learning theory is one thing but there is no substitute for practical experience. My top tip for getting a design to work is dont neglect the basics: Power supplies/grounding and decoupling, interface levels and drive strengths (both externally and between components), clocks an resets, signal termination.
Rach
