GAS ARM config/tc-arm.c

[Michael Kirkpatrick]

I am currently working on a research project that includes adding a new 
instruction to the ARM architecture.  I've found the places that I need 
to modify, but I'm not sure what the exact format of the code in GAS 
needs to be.  Specifically, I'm looking at the config/tc-arm.c file and 
the following lines:

#define T16_32_TAB                              \
[...]
  X(ldr,   6800, f8500000),                     \

and

 tCE(ldr,       4100000, ldr,      2, (RR, ADDR),    ldst, t_ldst),

Can someone provide me with a description of how the numbers 6800, 
f8500000, and 4100000 are derived?  I'm digging through the ARM 
reference manual, but would greatly appreciate a hint regarding what I'm 
looking at.

Thanks,
Michael Kirkpatrick