Can't Find Further Documentation on Spartan3E IO

Question

I am trying to find some further detail on the IO resources for a Spartan 3E.

Using ISE, when I open PlanAhead to look at the floor plan I see a lot of names, organization and acronyms that I do not understand. I have read the IOB sections in both the spartan 3 family-manual and the spartan 3E family guide. Neither provided these answers.

Apologies for asking multiple questions in a single post but specifically I would like to know:

1. Why are there blank pads? I can't move my primitives to any pads that do not have a number (P2, P3). What are they used for and can I use them for anything?
2. The Pads that do have numbers have a large marking (ex. P98) then in small letters (ex. Pad107). What is the difference? What do each actually mean and why does the order seem to not follow a simple cumulative pattern around the device?
3. What is a tile?
4. What does DIFFS and DIFFM mean and what is the difference?
5. The site properties mentions RPM grid. What is that? The manual talks about Relationally Places Macros but that's for programming the device.

Are there any good resources for learning this more, hands on knowledge, aside from the manuals?

Answer 1

What about Spartan-3 Generation FPGA User Guide (UG331)?

1.:
Blank pads might be other pin types e.g. VCC, GND, JTAG, ... Note that unused entities are not labeled.

2.:
Big chips use 2 or more coordinate systems. - Pad107 overall pad number - P98 pin number (pin 98)

3.:
A tile is a sub-region.

4.:
DIFFM means differential master.
DIFFS means differential slave.

5.:
RPM = Relationally Places Macros
You should check your documentation for relative placement rules and so on.