Not really useful yet...

PC, SP
IX, IY
IXH, IXL, IYH, IYL
AF, BC, DE, HL
A, F, B, C, D, E, H, L
AF', BC', DE', HL'
A', F', B', C', D', E', H', L'
MPTR or WZ (for MEMPTR register)
IR
I, R
IM, IFF1, IFF2
MRA, MWA - mem read addr, mem write addr
MRV, MWV - mem read value, mem write value

PRA, PWA - port read addr, port write addr
PRV, PWV - port read value, port write value
- can use IN, OUT in place of PRA, PWA

P0 - page at #0000 (0-7 or #FF for ROM)
P1 - page at #4000 (0-7 or #FF for ROM)
P2 - page at #8000 (0-7 or #FF for ROM)
P3 - page at #C000 (0-7 or #FF for ROM)
PAGING - combination of P0-P3 combined in 16 bits, so only #F for ROM bits
         ie: PAGING = #F527 is ROM at #0000, page 5 at #4000, page 2 at #8000, page 7 at #C000

TS - current T-State counter (up to 65535 only :p)

SNOW - snow effect active? (0 or 1)
SCREEN - active display on 128K models. (0 or 1)
BORDER - current border colour (0-7)
FRAMEINTS - current acknowledged interrupts counter (=1 at next interrupt in current frame or next interrupt after EI, > 1 for next retriggered interrupt)
AYSEL - currently selected AY register

FDC0 - FDC8 - current FDC parameters specific to individual +3 drive controller commands.


Currently all breakpoint conditions can only be specified as conditions that must all be True (as if all results were ANDed together, but without an AND operator) 
Examples:
pc>=32768
hl=de b>128 b <= 255
(23560)=13
(32768.w) = ix iy!=23610

All can be given as one-shot "stop" breakpoints in the command parser, overriding all other conditions until the debugger next opens
stop snow=1
stop pc=0
stop (pc)=#c7 (RST 0 about to be executed)
stop (pc.w)=#b0ed (LDIR about to be executed, little endian!)
stop (pc.w)=#b0ed de>=49152 (LDIR about to be executed, check for legal DE write address range)
stop mwa>=23296 mwa<23552 (if you wanted to find code inadvertently writing to a mem range)
stop P3=7 mwa>=#c000 (what's writing to bank 7 in error)
stop out&1=0 pwv&#10>0 (write to ULA port with speaker bit high)
