Motorola MC14500B Machine CodeMotorola MC14500B Machine Code, 2 bytes
5 OR the register with input from the data bus 8 Write the register to the data bus E Skip next instruction if register is zero C Jump
The Motorola MC14500B is a 1-bit microcontroller; it has a one 1-bit register and a 1-bit data bus. Since the opcodes are 4 bits each, there are only sixteen; half of them carry out a logical operation between the register and the bit on the data bus.
The jump instruction sets a jump flag; when no address is provided, it is common to set the program counter to 0. If the input bit was zero, the processor will not jump, but if. If the input bit was 1, the processor jumps back to the start. Sincestart; since we're
ORing with input, it doesn't matter what the input signal is afterwardsafterwards—the register will then be 1 forever.
As is conventional, the register is initialized to 0.
A list of the opcodes can be found on the data sheet, or here.