PROGRAM TRACING DEVICE

PURPOSE:To perform a program tracing process at a high speed, by appointing the writing in and reading out from a memory under an endless condition by one point by means of a counter and connecting the memory with a data bus through a gate. CONSTITUTION:When the address alphaAB of a program tracing device 10 is transmitted to an address bus (AB) 11 from a computer 9, a decoder 20 detects this and makes a signal 41 high level. When a strobe signal (SBT) 14 successively becomes high level, an AND gate 40 is turned on and, since a read/write signal (R/W) 13 is low level, another AND gate 60 is turned on. When the AND gate 60 is turned on, a gate 80 is opened and data are transmitted to a memory 90 from a data bus (DB) 12. A counter 30 indicates a memory writing point and increases the writing point one by one whenever the writing is made. Thus the counter 30 appoints endlessly the writing point in the memory. Since the R/W13 is high level when data are read out from the memory 90, an AND gate 50 is turned on and the data of the memory 90 are sent to the computer 9 through a gate 70 and DB12.