JPH05173833A - Signal trace circuit - Google Patents

Abstract

PURPOSE:To reduce the load of a CPU by eliminating a need of a signal trace program at the time of signal trace. CONSTITUTION:This circuit consists of a signal selecting part 3 which compares and collates a desired bit pattern signal 103 and a signal 101 as the trace object with each other and outputs a select signal 102 in the case of coincidence between both signals, a RAM 2 where only the desired bit pattern signal of the signal as the trace object is written with the select signal as the write signal, and a monitor part 1 which reads out the desired bit pattern signal written in this RAM and displays it on a display part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal trace circuit for tracing only a desired signal from signals to be traced.

[0002]

2. Description of the Related Art Generally, in a system using a CPU,
There is a method of tracing signals to confirm the signal contents as one means of debugging system hardware and software.
As a method of tracing such a signal, conventionally, a signal trace program is created in a software program of the system, and the signal trace program is executed by the CPU so that a desired bit is selected from the signals to be traced. A method has been proposed in which only a pattern signal is selected and a desired bit pattern signal is displayed on a display unit.

[0003]

In the conventional signal tracing method described above, a desired bit pattern signal is displayed on the display unit by a software program processed by the CPU in the system. Depending on the software processing, the load on the CPU increases and various processing efficiencies other than the signal trace program processing decrease. Further, the ratio of the signal trace program processing to the entire soft program capacity cannot be ignored.
An object of the present invention is to provide a signal trace circuit that reduces the load on the CPU by eliminating the need for a signal trace program.

[0004]

A signal trace circuit according to the present invention comprises a signal selecting section for comparing and collating a desired bit pattern signal with a signal to be traced and outputting a selection signal when both signals match. A RAM is provided for writing only a desired bit pattern signal from the signals to be traced using the selection signal as a write signal, and a monitor unit for reading out the desired bit pattern signal written in the RAM and displaying it on the display unit. .

[0005]

According to the present invention, by using the selection signal output from the signal selection unit as the write signal, only the desired bit pattern is written in the RAM, and the written signal is read by the monitor circuit. It is possible to display only the desired bit pattern.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. A signal trace circuit includes a monitor unit 1, a RAM 2, a signal selection unit 3 for selecting a desired bit pattern signal, and a display unit 5. . The signal selection unit 3 includes a comparison and collation circuit 4 that compares and collates the trace target signal 101 and the desired bit pattern signal 103 to be traced.
When 03 is selected, the selection signal 102 is generated at the timing shown in FIG. Further, the RAM 2 writes the signal on the signal 101 to be traced at the rising edge of the selection signal 102. On the other hand, the monitor unit 1 reads out the desired bit pattern signal 104 stored in the RAM 2 at the timing shown in FIG. 2B in which no signal is written to the RAM 2 by the selection signal 102, and the read signal 104 is displayed on the display unit. It is supposed to be displayed at 5.

Therefore, the signal selection unit 3 outputs a selection signal 102 when the signal 101 to be traced matches the bit pattern signal desired to be traced, and writing to the RAM 2 is performed based on this selection signal 102. Therefore, only the desired bit pattern signal 103 among the signals 101 to be traced is written in the RAM 2. Then, since only the written bit pattern signal 103 is read by the monitor unit 1 at the next timing, the desired bit pattern signal is displayed on the display unit 5.

[0008]

As described above, according to the present invention, the selection signal output from the signal selection unit is used as the write signal in the RAM.
By writing to the RAM, only the desired bit pattern signal is written to the RAM, and if the monitor unit reads it and displays it on the display unit, the signal trace becomes possible without using the signal trace processing program, and the load applied to the CPU is increased. And the processing efficiency in the CPU can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal trace circuit of the present invention.

FIG. 2 is a waveform diagram showing timings of writing and reading signals to and from the RAM in the signal trace circuit of FIG.

[Explanation of symbols]

 1 monitor section 2 RAM 3 signal selection section 4 comparison and collation circuit 5 display section

[Procedure amendment]

[Submission date] November 2, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

Claims (1)

[Claims] 1. A signal trace circuit for selecting only a desired bit pattern signal from signals to be traced and displaying the desired bit pattern signal on a display unit,
The desired bit pattern signal and the signal to be traced are compared and collated, and a signal selection unit that outputs a selection signal when both signals match, and a signal to be selected from the signals to be traced, which is the selection signal as a write signal. And a monitor section for reading out a desired bit pattern signal written in the RAM and displaying it on a display section.