I am in the early stages of a fairly ambitious project and trying to limit the number of pins used.
The project will use several different "add-on" modules and at least one 74HC595 shift register.
As some of the "modules" require a clock-out pin, can these be all from the one output of my Nano?
I will be using a MAX31855, an RTC, an SD Card Reader, and two TM1637 4x7seg displays.
Please advise if this is not in the correct forum, thanks, Ron.
Ron47Walker:
I am in the early stages of a fairly ambitious project and trying to limit the number of pins used.
No doubt.
Ron47Walker:
As some of the "modules" require a clock-out pin, can these be all from the one output of my Nano?
You need to do much better than that!
Which modules, what sort of "clock" do they use? 
Ron47Walker:
Please advise if this is not in the correct forum, thanks, Ron.
Near enough. 
Typically where there is a clock in pin there is also an enable pin. The general idea is to connect a single clock shared across all the clock in pins and use the enable pin to tell the board that it should respond to the clock, while all the others ignore the clock.
Without more information it's impossible to be more specific.
I will be using a MAX31855, an RTC, an SD Card Reader, and two TM1637 4x7seg displays.
So that will be a no then. You have a mixture of SPI and I2C so while some can share the all the pins on the I2C devices and all of the pins on the SPI devices with a separate chip select for each device.
However when it comes to the TM1637, you can shair none of the pins because although it looks like an I2C device it is not.
From the TM1637 data sheet:-
(Note: The communication method is not equal to 12C bus protocol totally because there is no slave address).
Ron47Walker:
I will be using a MAX31855, an RTC, an SD Card Reader, and two TM1637 4x7seg displays.
The MAX31855 is SPI, the SD Card reader will be SPI, and the 74hc595 is SPI. So they can all share the clock pin, data-in and data-out pins. Some RTC boards have SPI, but many are I2C only, so make sure you get an SPI compatible one such as DS3234. Replace the displays with something driven by max7219 and you are all-SPI.
But... you asked about clock outputs? All these devices have clock inputs, not clock outputs...