How to import an image as pure black and white

[LaserPicStore]

I'm pretty new to photoshop, so sorry if this is something simple, but I have searched high and low and cannot find a solution.

I have an image that I have dithered in other software. This means that the image is made up of only black and white dots. If I drag the image into Photoshop, it innitially shows up as just black and white dots, but as soon as the image is placed it becomes a greyscale version of the image with hues of grey surrounding the black and white dots. 
For what I want to do, I need it to be pure black and white like the original image. How can I accomplish this?

What I have tried so far:

I ensured that the canvas size is the exact same as the image, so that the pixels should correspond.

I tried playing around with Image -> Mode settings, but none of those make any difference.

Please Help.

Thank you

[Semaphoric]

What is the file format the other software saves in, and what are the pixel dimensions of your image? Are there any other layers in your Photoshop document?

[Stephen Marsh]

.I tried playing around with Image -> Mode settings, but none of those make any difference.

Please Help.

Thank you

By @LaserPicStore

Open the image, don't drag or place it.

What is it's colour mode?

You can always use a threshold adjustment to force this, or, if needed, you can go to greyscale mode and then to bitmap mode using a 50% threshold conversion.

[LaserPicStore]

Thank you for that. Opening the image directly in Photoshop and then copying it into the design fixed the issue.

The problem is that it's in a Smart Object, so was hoping it would work by just replacing content, or drag and drop, like it does with anything else, but I can make it work this way as well.

[Stephen Marsh]

Thank you for that. Opening the image directly in Photoshop and then copying it into the design fixed the issue.

Great!

You didn't answer my previous question, regarding the colour mode of the original image when you open it.

The problem is that it's in a Smart Object, so was hoping it would work by just replacing content, or drag and drop, like it does with anything else, but I can make it work this way as well.

By @LaserPicStore

Smart object layers will convert the placed content into the containing document colour mode, so a "child" bitmap mode smart object will display as a layer in the "parent" document colour mode (RGB, CMYK etc). Editing the smart object will open it in the original bitmap mode. So you probably still need to clip a Threshold adjustment layer to the smart object layer to ensure it only has bi-tonal levels.