system lzpmcn with the print data supply system as described above the address operation processing by the print output address operation controller lzctr is not an sequential execution synchronized with the clock signal clk only rather the address operation is synchronized with the state of the laser printer machine system lzpmcn indicated by the linechanging signal cr the page changing signal cp and the print address output request signal prreq therefore print output address operation control is accomplished by a relatively small scale circuit utilizing the state signal of the laser printer machine system lzpcn this small scale circuit control does not require any complex timing adjustment circuits for adjusting the address control to any change in the state of the laser printer machine system lzpmcn fig7 is a block diagram detailing one example of the refresh address generator rfgen described above in fig7 symbol rfint represents a refresh interval register which contains the refresh interval necessary to maintain the data in the dram of the frame buffer memory fbm the initial value of the rfint is set by the host processor hmpu symbol itvcnt represents an interval counter which is normally incremented once per memory cycle the value of this interval counter itvcnt is compared with.