Probe for in-circuit emulator with flexible printed circuit board

A probe for an in-circuit emulator for use in program verification and debugging during development of an equipment using a microcomputer is disclosed. The probe is formed by a flexible printed circuit board on which a plurality of conductive lines and a plurality of solder-connecting elements are provided. The conductive lines and the solder-connecting elements are electrically connected through a plurality of through-holes provided in the flexible printed circuit board. The solder-connecting elements of the probe are solder-connected to conductive lines of a target board to be emulated. The in-circuit emulator does not require a dummy chip, which makes the probe simple in its structure and economical in the fabrication thereof.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an in-circuit emulator, and more 
particularly to a probe using a flexible printed circuit board. 
2. Description of the Related Art 
For the purpose of assisting in the understanding of the present invention, 
a conventional probe for the in-circuit emulator of the type relevant to 
the present invention is first explained with reference to the related 
drawings. 
FIG. 1 shows in sectional view a conventional probe of the kind to which 
the present invention relates. As shown in FIG. 1, a target board 
conductor line 12 is provided on a target board 10 and a dummy chip 18 to 
which a dummy chip lead 14 is fixed is provided on this target board 
conductor line 12. The dummy chip 16 detachably receives a probe head 18 
from which a flat cable 19 is drawn out. 
FIG. 2 shows in perspective view a microcomputer program development system 
to which the probe shown in FIG. 1 is connected. As seen in FIG. 2, the 
target board 10 carrying thereon the dummy chip 16 is prearranged, and the 
flat cable 19 having the probe head 18 at the foremost end is connected to 
an in-circuit emulator 20 which in turn is connected to a personal 
computer 22. 
First, an object of using an in-circuit emulator (hereinafter referred to 
as an "ICE") is briefly explained. For producing an equipment using a 
microcomputer, it is required to prepare a hardware of the equipment and a 
software for the microcomputer for controlling the hardware. In order to 
realize the functions brought out by specifications of the equipment, the 
functions to be assigned to the hardware and those to the software are 
sorted out and the former and the latter are separately designed and 
organized. The hardware and the software thus organized separately from 
each other are put together and are caused to operate together, whereby 
whether the equipment operates in a way to satisfy the specifications is 
verified. 
The ICE 20 is an equipment used for making the above verification, which 
provides operational environments for the software to be executed and 
verification supporting functions such as a function to execute sequential 
instructions step by step and a function to interrupt execution of 
instructions when certain conditions are met. The ICE 20 also provides, as 
a hardware function, a function to input to and output from the probe head 
18 a signal which is the same as the signal inputted to and outputted from 
an external terminal of the microcomputer in the equipment under 
development. Thus, when the probe is connected to the hardware of the 
equipment under development and the software is executed on the ICE 20, 
the various operations expected from the microcomputer on the basis of the 
software are emulated by the ICE 20, so that the same signal as outputted 
by the terminal of the microcomputer is outputted from the terminal of the 
probe and the same control as effected by the microcomputer is realized. 
In the ICE 20 as described above, the conventional probe of the ICE 20 
employs an arrangement wherein its tip portion has a dummy chip 18 (shown 
in FIG. 4) the shape of which is the same as the shape of the terminal of 
the microcomputer to be emulated. Where the shapes are the same in this 
way, the circuit patterns of the target board conductor 12 of the printed 
circuit board (as shown in FIG. 3) which is a part of the hardware of the 
equipment under development remain fixed or unchanged. Thus, the purpose 
of such arrangement is to complete the development of the equipment as a 
finished equipment by removing the probe of the ICE and then mounting the 
microcomputer in its place. That is to say, in this arrangement, the 
operational reliability of the equipment can be ensured because the 
pattern of the printed circuit after the completion of the verification of 
the functions of the equipment is in its finished state and undergoes no 
further changes. 
FIG. 3 shows in plan view a plurality of circuit patterns provided on a 
conventional target board and FIG. 4 shows also in plan view a state in 
which a dummy chip 16 is soldered on the target board 10 shown in FIG. 1. 
As seen in FIG. 3, the leads 14 of the dummy chip 16 are arranged in all 
four directions and the conductive lines 12 on the target board 10 are 
electrically connected to the leads 14, respectively. 
In the conventional probe of the ICE explained above, it is required that 
the dummy chip 16 at the foremost end portion of the probe be made in 
conformity with the shape of the terminal of the microcomputer to be 
subjected to emulation. 
In recent years, kinds of microcomputers have become diversified and, 
particularly in microcomputers used for control purposes, there is an 
increasing trend wherein the same function is applied to a plurality of 
terminal shapes or a given function is added or eliminated depending on 
needs in the development of equipment. 
In order to meet the changing needs in the development of equipment using 
microcomputers, it is desired that, in the ICE, too, the dummy chip 16 at 
the foremost end of the probe be improved. 
However, since the dummy chip 16 normally employs at its body an 
engineering plastic and has a terminal portion made of metal foils, it is 
necessary to make a metal mold specific to the body and make the terminal 
portion mostly by hand. This is a disadvantage in that the fabrication 
thereof is not efficient, is costly and involves a long time. 
Also, it must be noted that in recent years there is an increasing trend 
for spaces between terminals of a microcomputer to be reduced, and this 
makes it impossible to have the dummy chip 16 formed by the conventional 
method, or if formed, the chip thus formed frequently does not have 
sufficient strength for practical use. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to overcome the 
problems existing in the conventional arrangements as described above and 
to provide an improved probe for an in-circuit emulator which requires no 
dummy chip and which is simple in its structure and is not costly in the 
fabrication thereof. 
According to one aspect of the invention, there is provided a probe formed 
by a flexible printed circuit board and connected to an in-circuit 
emulator for use in program verification and debugging during development 
of an equipment using a microcomputer, the probe comprising: 
a plurality of conductive lines which are provided on the flexible printed 
circuit board and coupled to the in-circuit emulator; and 
a plurality of solder-connecting elements which are solder-connected to 
conductive lines provided on a target board that is subjected to emulation 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, preferred embodiments of the invention will be explained with 
reference to the accompanying drawings. It is to be noted that, throughout 
the following explanation, similar reference numerals or symbols refer to 
the same or similar elements in all the figures of the drawings. 
FIG. 5 shows in plan view a flexible printed circuit board 50 according to 
a first embodiment of the invention. As seen in FIG. 5, the printed 
circuit board 50 constitutes electric circuitry with the upper and back 
surfaces of a flexible board being etched and provided with a number of 
conductive lines 56. 
In the specific example shown in FIG. 5, the printed circuit board 50 has a 
card edge portion 51 at one edge, a square window 52, four screw holes 53, 
and nine through-holes 54 at each side around the square window 52. Thus, 
there exist thirty six through-holes 54 around the square window 52. The 
conductive lines 56 on the upper surface and those on the back surface are 
interconnected through these through-holes 54. 
More specifically, the probe for the ICE 20 in this embodiment of the 
invention utilizes the flexible printed circuit board 50 with a 
solder-connecting portion 58 (seen in FIG. 6) which corresponds to an 
under surface of a target IC terminal, being provided on the back surface 
of the flexible printed circuit board 50. The probe includes the 
through-hole 54 through which the conductors 56 at the upper surface and 
at the back surface of the flexible printed circuit board 50 are 
electrically connected together, the screw holes 53 for positioning and 
keeping the probe in place, and the window 52 for facilitating soldering 
the flexible printed board 50 and the target board 60 together. 
The conductive lines 56 are led around edge portions of the flexible 
printed circuit board 50 for having the in-circuit emulator to be 
connected thereto, with the card edge portion 51 being formed at one edge 
portion. The conductive lines 56 are connected to the ICE 20 through the 
connector 57 and the flat cable 59 as seen in FIG. 7. 
FIG. 6 shows in sectional view a state in which the printed circuit board 
50 is mounted on the target board 60, the sectional view taken along A--A' 
line in FIG. 5. As seen in FIG. 6, the flexible printed circuit board 50 
shown in FIG. 5 is soldered by the solder-connecting portion 58 to the 
target board conductive lines 62 on the target board 60, thereby 
establishing electric conduction therethrough. Thus, a signal from the 
conductor 62 on the target board 60 is allowed to pass through the 
solder-connecting element 58, the through-hole 54 and the conductors 58 
and transmitted from the card edge portion 51 to the ICE 20 through a 
connector 57 and the flat cable 59. A signal from the ICE 20 to the target 
board 60 follows a path in reverse to the above. 
FIG. 7 shows in perspective view a program development system utilizing the 
target board and the printed circuit board shown in FIG. 6. The personal 
computer 70 controls the ICE 20. The emulator signal passes through the 
flat cable 59 and, via the connector 57, passes through the conductive 
lines 62 (seen in FIG. 5) of the flexible printed circuit board 50 for 
controlling the circuitry on the target board 60. 
In the embodiment shown in FIG. 5, the screw holes 53 serve to positioning 
and securing the flexible printed circuit board 50 on the target board 60 
and the window 52 facilitates soldering of the flexible printed circuit 
board 50 onto the target board 60. 
As explained above, since the probe is in the form a flexible printed 
circuit board 50, the probe does not require the dummy chip 16 unlike in 
the conventional arrangement and the probe itself is structurally simple 
and is markedly cost saving as shown in the following table. 
TABLE 
______________________________________ 
CONVENTIONAL 
INVENTION 
______________________________________ 
Cost of dummy-chip mold 
800,000 0 
Cost for making dummy- 
20,000 0 
chip 
Cost for making probe 
45,000 10,000 
TOTAL 865,000 10,000 
______________________________________ 
Further, the fact that the probe is structurally simple also means that it 
provides sufficient strength in the actual structure obtained. 
Also, since the forming of conductive lines 56 on the flexible printed 
circuit board 50 by means of etching is comparatively simple and can be 
done in a short period of time, the invention is fitted to a wide variety 
of applications, a small quantity fabrication, and a short term 
fabrication. 
FIG. 8 shows in perspective view a probe for an in-circuit emulator 
according to a second embodiment of the invention. As seen in FIG. 8, the 
flexible printed circuit board 80 is connected to the target board 90 
through the solder-connecting element 88, the conductive lines 86 are 
connected at the card edge portion 81 to the connector 87 from which the 
flat cable 89 is drawn out. 
The probe according to this second embodiment is adapted to be used for 
microcomputers having leads of dual in-line package type (DIP) 
semiconductor devices. For the DIP type, the probe according to this 
second embodiment, which is more compact and easier in use, is better 
suited than the probe according to the first embodiment. 
While the invention has been described in its preferred embodiments, it is 
to be understood that the words which have been used are words of 
description rather than limitation and that changes within the purview of 
the appended claims may be made without departing from the true scope and 
spirit of the invention in its broader aspects.