I used the basic robotic test bed and added a driver for RC servos.
I believe that the monitor program allows the user to modify a memory location
(just registers on the 1200) that sets the RC servo position.

usart.asm   Interrupt activated polled I/O
analog.asm   Analog driver for photo cell "eyes"
main.asm   Top level
brains.asm   Robot logic (not used here)
cpu.asm   Hardware initialization code
monitor.asm   State Driven monitor
Servo.asm   The driver
timer.asm   Manages timer hardware and calls tasks
s1200def.INC   My version of this file from ATMEL