The AXTR does not have a local interface chip, and there
are no user addresses.  However, the AXTR fully utilizes
the generic address space, using the "slopebits" registers
and the (set/clear) fake data register, which is often not
done on other boards.

The slope bits registers are at addresses of the form
027xxy
as shown in the a32 address map.  There are four data
banks (with y=0,4,8,c) containing slopes and the corrbit 
from key wires 1/2, 3/4, 5/6, and 7 (odd key wire in the 
lowest 16 bits, even key wire in upper 16 bits).  
There are 14 slope bits, 1-5 inner plus 1-9 outer.  Data 
bit 0 contains inner slope bit 1.  The bits are filled 
sequentially up the data lines, with outer slope bit 9 in 
data bit 13.  Data bit 14 contains the corrbit, the result 
of correlating the inner and outer slopes.  Data bit 15 is 
not used.

The set/clear fake data register is used to send fake data
(corrbits) off of the board to the AXPR.  The addresses
are as given in the a32 address map.  Data lines 16-22 are
used when setting the fake data.  The axtr_submenu in 
gentest will shift your input data up to the correct data
bits.