Control Lines

Cnt – Count – Increment the value of the Program Counter by 1.

Lpcl – Load Program Counter Low – Copy the value on the Data Bus to the low buffer of the

Program Counter.

Lpcl – Load Program Counter High – Copy the value on the Data Bus to the High buffer of the

Program Counter.

Xpc – Transfer Program Counter – Change value of Program Counter to be the value specified

by the Program Counter Buffer.

Lm – Load MAR – Put the value of the Program Counter onto the Address Bus.

Lml – Load MAR Low – Copy the value on the Data Bus to the low buffer of the MAR.

Lmh – Load MAR High – Copy the value on the Data Bus to the high buffer of the MAR.

Xm – Transfer MAR – Put the value of the MAR’s buffer onto the Address Bus.

Clm – Clear MAR – Clear the buffer of the MAR.

Me – Memory Enable – Activate the Memory Location specified by the value on the Address

Bus.

Rd – Read – Copy the contents of the activated Memory Location onto the Data Bus.

Wr – Write – Copy the value on the Data Bus to the activated Memory Location.

Io – Input/Output – Activate the Input or Output device specified by the Address Bus.

Lr – Load Register – Copy the value on the Data Bus to the Instruction Register.

Dcd – Decode – Interpret what Action is specified by the code that was placed into the

Instruction Register.

LdA – Load A – Copy the value on the Data Bus into Register A.

EnA – Enable A – Copy the contents of Register A onto the Data Bus.

Shl – Shift Left – Shift the bits of Register A one place to the left. Place a 0 into the Least

Significant Bit (LSB).

Shr – Shift Right – Shift the bits of Register A one place to the right. Place a 0 into the Most Significant Bit (MSB).

Add – Add – Perform the addition of the value on the Data Bus to the contents of Register A.

Place the Answer in Register A and set the Flags appropriately in the Flags Register.

Sub – Subtract – Perform the subtraction of the value on the Data Bus from the contents of

Register A. Place the Answer in Register A and set the Flags appropriately in the Flags

Register.

Cmp – Compare - Perform the subtraction of the value on the Data Bus from the contents of

Register A. Set the Flags appropriately in the Flags Register. Do Not Change the

contents of Register A to provide the Answer.

And – And – Perform a bitwise Logical AND operation between the value on the Data Bus and

the contents of Register A. Place the Answer in Register A and set the Flags

appropriately in the Flags Register.

Or – Or – Perform a bitwise Logical OR operation between the value on the Data Bus and

the contents of Register A. Place the Answer in Register A and set the Flags

appropriately in the Flags Register.

Xor – Xor – Perform a bitwise Logical XOR operation between the value on the Data Bus and

the contents of Register A. Place the Answer in Register A and set the Flags

appropriately in the Flags Register.

LdB – Load B – Copy the value on the Data Bus to Register B.

EnB – Enable B – Copy the contents of Register B to the Data Bus.

InB – Increment B – Increase the value of the contents of Register B by 1.

DeB – Decrement B – Decrease the value of the contents of Register B by 1.

LdC – Load C – Copy the value on the Data Bus to Register C.

EnC – Enable C – Copy the contents of Register C to the Data Bus.

InC – Increment C – Increase the value of the contents of Register C by 1.

DeC – Decrement C – Decrease the value of the contents of Register C by 1.

LdD – Load D – Copy the value on the Data Bus to Register D.

EnD – Enable D – Copy the contents of Register D to the Data Bus.

InD – Increment D – Increase the value of the contents of Register D by 1.

DeD – Decrement D – Decrease the value of the contents of Register D by 1.