- all coordinates are in units of 1/40 mm (1/1016 in)
- bounds are (0,0,-???) - (6096,4064,???) (??? depends on Z0)
- explicit absolute/relative commands (like PA) set default for others (like Z)
- despite group names, any command may be issued at any time

mode1

@ down(,up)             set tool down (<= 0), tool up (>= 0) Z height
D x1,y1(,x2,y2...)      Draw: absolute move with tool down
F speed                 Feed: set tool-down XY-speed in mm/sec (float ok)
H                       Home: absolute 0,0,top + stop motor
I dx1,dy1(,dx2,dy2...)  Increment: relative move with tool down
M x1,y1(,x2,y2...)      Move: absolute move with tool up
R dx1,dy1(,dx2,dy2...)  Relative: relative move with tool up
V speed                 Velocity: set Z-speed in mm/sec (float ok)
W time                  dWell: set msec to dwell before commands
Z x1,y1,z1(,...)        xyZ: 3D move (abs/rel) at Z-speed (for all axes)

mode2

DF                      DeFaults: reset PA, VS, !VZ, !DW, !MC, !PZ
IN                      INitialize: DF + home + PU + stop motor + reset coords
PA x1,y1(,x2,y2...)     Plot Absolute: absolute move (use last PU/PD)
PD x1,y1(,x2,y2...)     Pen Down: move with tool down (use last PA/PR)
PR x1,y1(,x2,y2...)     Plot Relative: relative move (use last PU/PD)
PU x1,y1(,x2,y2...)     Pen Up: move with tool up (use last PA/PR)
VS speed                Velocity Select: set tool-down XY-speed in mm/sec

Common

!DW time                DWell: set msec to dwell before commands
!MC n                   Motor Control: 0 = off, !0 = enabled at next move
!PZ down(,up)           Pen Z: set tool down (<= 0), tool up (>= 0) Z height
!VZ speed               Velocity Z: set Z-speed in mm/sec (float ok)
!ZM z                   Z Move: move to specified height (at current abs/rel)
!ZZ x1,y1,z2(,...)      move to 3D coordinates (at current abs/rel)