
* structure definition

 base 0
spacia rmb 2 acia address
spiptr rmb 2 input ptr
spoptr rmb 2 output ptr
spcntr rmb 1 char counter
spbfst rmb 2 buffer start
spbfen rmb 2 buffer end
spstat rmb 1 status
spxoff rmb 1 holding for xoff
spspcl rmb 1 ttyset byte indicating XON/XOFF

SPSZ equ * structure size
