PARAMETER ARITHMETIC UNIT

PURPOSE:To simply recognize a parameter relating to the period of video data by enabling a host computer to calculate automatically the parameter relating to the period of a signal outputted by the host computer by merely setting the number of horizontal and vertical valid picture elements of an output signal. CONSTITUTION:When a switch 20 is closed, a printer 101 is set to the parameter setting mode and a CPU 5 turns on a relay switch 13. Furthermore, the CPU 5 allows a reference clock generator 7 to generate a sampling clock. The user enters horizontal and vertical picture element numbers Nh, Nv of a video signal of the computer 1 by using a panel 6. Then the host computer 1 provides an output of a reference video signal and the signal is given to a synchronizing separator circuit 4 of the printer 101 from a G terminal 16, the circuit 4 separates the input signal from an HD terminal 18 and a VD terminal 19 into a horizontal synchronizing signal and a vertical synchronizing signal and they are given to the CPU 5, and stored in a frame memory 3. The CPU 5 allows a reference signal from the means 7 to be stored in the memories 3, 22 and calculates the parameter relating to the period of the signal outputted from the computer 1 based on the horizontal and vertical picture element numbers and the reference signal in the memory 3.