ASMB,A,B,L

      HED ** Small Light Chaser **
* by Tim Riker <Tim@Rikers.org>
      ORG 10B
S     EQU 1

CHASE CLB,CCE      B=0, E=1

* This instruction gets modified!
ROT   ELB          rotate E and B left/right 1
      OTB S        B to S

* delay loop
      LDA DELAY    Get delay in A
      CMA          2's complement A
LOOP  INA,SZA      Increment A, Skip one if A=0
      JMP LOOP     Delay some more

      CLE,SZB      Clear E, Skip one if B=0
      JMP ROT      Rotate another bit

* change direction
      LDA MAGIC    Load XOR pattern
      XOR ROT      XOR instruction
      STA ROT      Store new instruction
      JMP CHASE    Start rotating in the other direction

MAGIC OCT 000300   XOR diff from ELB/ERB
DELAY OCT 017777   amount to delay