Probe terminating apparatus for an in-circuit emulator

In a probe terminating apparatus, ground terminals, power supply terminals, and open terminals are provided on a print circuit board, and a ground potential applying terminal and a power supply voltage applying terminal are also provided on the print circuit board. In addition, a pull-down resistance apparatus is inserted to be connected between each of the ground terminals and the ground potential applying terminal, and a pull-up resistance apparatus is inserted to be connected between each of the power supply terminals and the power supply voltage applying terminal. Terminals of an evaluation microcomputer in an in-circuit emulator are connected to the ground terminals, the power supply terminals, and the open terminals by the connection of a probe and an IC socket, or connectors. The probe is connected to the terminals of the evaluation microcomputer, and the IC socket is connected to the ground, power supply and open terminals of the probe terminating apparatus.

FIELD OF THE INVENTION 
The invention relates to a probe terminating apparatus for an in-circuit 
emulator, and more particularly to, an apparatus for terminating terminals 
of an evaluation microcomputer in an in-circuit emulator. 
BACKGROUND OF THE INVENTION 
A hardware system such as a refrigerator, a car, a watch, etc. is 
controlled in operation by a microcomputer mounted therein. In order to 
assist the development of such a hardware system, an in-circuit emulator 
which comprises an evaluation microcomputer and a memory for a program is 
used. The evaluation microcomputer evaluates a microcomputer mounted in a 
hardware system (defined "hardware system to be evaluated in operation" 
hereinafter). Even prior to the completion of a hardware to be evaluated 
in operation, therefore, the development and evaluation of a program to be 
stored in the hardware can be carried out in an in-circuit emulator by 
using an evaluation microcomputer and a memory included therein. In the 
development and evaluation of the program, terminals of the evaluation 
microcomputer must be set to be specifically high and low not to prevent 
the program form being executed. 
For the other reason, most of microcomputers are designed by using CMOS 
process technology which is characterized in that power consumption is 
low. Due to the characteristics of CMOS devices, input terminals which are 
not connected to any terminals must be set to be specifically high and 
low. 
A first conventional method for setting non-connected terminals of an 
evaluation microcomputer to be high and low is that the non-connected 
terminals are connected to an IC socket provided in an in-circuit emulator 
by a probe connected via a cable to the non-connected terminals. 
A second conventional method for setting non-connected terminals of an 
evaluation microcomputer to be high and low is that the non-connected 
terminals are pulled up to a power supply and down to ground by using 
pull-up and down resistances. 
A third conventional method for setting non-connected terminals of an 
evaluation microcomputer to be high and low is that the non-connected 
terminals are connected to a power supply and ground by using selectors. 
However, there are disadvantages in the first to third conventional methods 
in that: 
the size is large, the construction is complicated, and the cost is high in 
the first conventional method, because the IC socket is provided in an 
in-circuit emulator; 
the electric characteristic is changed, and through-current flows through 
input gates to lower the reliability of a device in the second 
conventional method, because pull-up resistances connected to a signal 
line tends to differ in value from each other, and a potential on a signal 
line divided by resistances happens to turn both p- and n- transistors on; 
and 
a number of selectors must be provided, and a signal propagation delay 
occurs in the third conventional method, because a selector is provided on 
each signal line. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the invention to provide a probe 
terminating apparatus for an in-circuit emulator which is small in size, 
simplified in construction, and low in cost. 
It is a further object of the invention to provide a probe terminating 
apparatus for an in-circuit emulator no through-current flows through 
input gates, and the electric characteristics are not changed. 
It is a still further object of the invention to provide a probe 
terminating apparatus for an in-circuit emulator in which there is no 
necessity to have selectors, and no signal propagation delay occurs. 
According to the invention, a probe terminating apparatus for an in-circuit 
emulator, comprising: 
ground terminals, power supply terminals, and open terminals provided on a 
print circuit board; 
a ground potential applying terminal and power supply voltage applying 
terminal provided on the print circuit board; 
a pull-down resistance apparatus inserted to be connected between each of 
the ground terminals and the ground potential applying terminal; 
a pull-up resistance apparatus inserted to be connected between each of the 
power supply terminals and said power supply voltage applying terminal; 
and 
means for connecting terminals of an evaluation microcomputer to the ground 
terminals, the power supply terminals and the open terminals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Before describing a probe terminating apparatus for an in-circuit emulator 
of a preferred embodiment according to the invention, conventional probe 
terminating methods will be explained in FIGS. 1 to 4. 
FIG. 1 shows a first conventional in-circuit emulator 50 in which a first 
conventional probe terminating method is carried out. The in-circuit 
emulator 50 comprises print circuit boards 55 to 57 connected by connector 
59A and 59B, wherein an IC socket 54 is provided on the print circuit 
board 55, an evaluation microcomputer 52 and a connector 53 for connecting 
a probe 51 to the print circuit board 56 are provided on the print circuit 
board 56, and a memory 58 for storing a program to be developed is 
provided on the print circuit board 57. 
In operation, the probe 51 is connected to the IC socket 54, so that 
terminals of the probe 51, that is, terminals of the evaluation 
microcomputer 52 are set to be specifically high and low. At this state, a 
program to be developed is stored in the memory 58, from which the program 
is read to be executed for the development thereof by the evaluation 
microcomputer 52, and program developing result is displayed on a CRT (not 
shown) for a programmer. Thus, a developed program is stored in the memory 
58. 
On the other hand, a hardware system to be evaluated in operation such as a 
refrigerator, a watch a car, etc. is usually controlled by a microcomputer 
mounted therein. For the purpose of evaluating operation of the hardware 
system, the in-circuit emulator 50 is used under a state that the probe 51 
is connected to the hardware system. Thus, the program stored in the 
memory 58 is executed to control the hardware system by the evaluation 
microcomputer 52 in place of the microcomputer mounted in the hardware 
system. 
FIG. 2 shows a second conventional in-circuit emulator 60 is which a second 
conventional probe terminating method is carried out. The in-circuit 
emulator 60 comprises an evaluation microcomputer 61 having power supply 
terminals VDD and GND connected to a power supply 69A and ground 69B and 
input terminals 62 to 64, a connector 68 for connecting the evaluation 
microcomputer 61 via a probe 51 to a hardware system to be controlled by a 
microcomputer. 
In operation, the input terminals 62 to 64 are connected to be pulled up 
via resistance 65 to 67 to the power supply 69A, so that the input 
terminals 62 to 64 are set to be high. Thus, a program can be developed, 
even if the probe 51 is under non-connected state. 
FIG. 3 shows a hardware system 70 connected to the in-circuit emulator 60 
which is explained in FIG. 2, wherein like parts are indicated by like 
reference numerals between FIGS. 2 and 3. The hardware system 70 comprises 
a signal line 73 connected via a resistance 71 to a power supply 76, a 
signal line 75 connected via a resistance 72 to ground 77, wherein the 
signal line 73 is pulled up by a sum of the resistances 65 and 71, and the 
signal line 75 is at a potential divided by the resistances 67 and 72. 
FIG. 4 shows a third conventional in-circuit emulator 80 which comprises an 
evaluation microcomputer 81 having power supply terminal VDD and GND 
connected to a power supply 86 and ground 87, and input terminals 82, 83,- 
- -, and selectors 84, 85,- - - connected to the input terminals 82, 83,- 
- -. 
In operation, the input terminal 82 is set to be high, when the selector 84 
selects an X terminal, and it is connected to a hardware system to be 
evaluated, when it selects a Y terminal. On the other hand, the input 
terminal 83 is set to be low, when the selector 85 selects an X terminal, 
and it is connected to the hardware system, when it selects a Y terminal. 
Next, a probe terminating apparatus for an in-circuit emulator of a first 
preferred embodiment according to the invention will be explained in FIGS. 
5 according to the invention will be explained in FIGS. 5 and 6. 
In FIG. 5, the apparatus comprises an IC socket 20 provided on a print 
circuit board 10 into which plural connecting pins of a hardware system to 
be evaluated in operation are inserted, in ground potential terminals 11, 
power supply terminals 12 and open potential terminals 13 connected to the 
IC socket 20, a ground potential applying terminal 14 and a power supply 
voltage applying terminal 15 provided on the print circuit board 10, a 
pull-down resistance apparatus 16 connected between the ground potential 
terminal 11 and the ground potential applying terminal 14 by an 
interconnection 17, a pull-up resistance apparatus 18 connected between 
the power supply potential terminal 12 and the power supply voltage 
applying terminal 15 by an interconnection 19, and a fixing lever 1. 
In this apparatus, the IC socket 20 is of a PGA (pin grid array) type by 
which the terminals 11 to 14 are connected to a probe (not shown) of the 
in-circuit emulator. 
In operation, a probe 21 of the in-circuit emulator is connected to the IC 
socket 20, and a power supply cable 22 is connected to the power supply 
voltage applying terminal 15. As a result, the power supply potential 
terminal 12 is pulled up via the interconnection 19 by the pull-up 
resistance apparatus 18. 
The ground potential applying terminal 14 is for a terminal corresponding 
to a ground terminal of a microcomputer, and is connected via the probe 21 
to a ground potential in the in-circuit emulator. As a result, the ground 
potential terminal 11 is pulled down via the interconnection 17 by the 
pull-down resistance apparatus 16. 
On the other hand, the open terminal 13 is a terminal which is not 
connected to any interconnection. Therefore, terminals which are not 
required to be pulled up and down are connected to the open terminals 13. 
As described above, a probe of an in-circuit emulator is connected to the 
IC socket 20 of the probe terminating apparatus, so that an evaluation 
microcomputer in the in-circuit emulator is set at terminals to be 
specifically high, low and open. 
FIG. 7 shows a probe terminating apparatus for an in-circuit emulator of a 
second preferred embodiment according to the invention, and FIG. 8 shows 
the connection between the prove terminating apparatus and an in-circuit 
emulator, wherein like parts are indicated by like reference numerals 
between the first and second preferred embodiments. 
The second preferred embodiment only in that the IC socket 20 is replaced 
by connectors 30 and 31. 
The connectors 30 and 31 are connectors for connecting the in-circuit 
emulator 40 to the probe terminating apparatus 41. 
The in-circuit emulator 40 comprises print circuit boards 10A and 10B 
connected by a connector 59, wherein an evaluation microcomputer 52, 
connectors 42 and 43, and a power supply terminal 44 are provided on the 
print circuit board 10A, and a memory 58 for storing a program to be 
developed is provided on the print circuit board 10B. 
In operation, the connectors 30 and 31 of the probe terminating apparatus 
41 are connected to the connectors 42 and 43 of the in-circuit emulator 
40, and the power supply voltage applying terminal 15 of the probe 
terminating apparatus 41 is connected to the power supply terminal 44 of 
the in-circuit emulator 40 by a power supply cable 45. As a result, 
terminals of the evaluation microcomputer 52 are set to be specifically 
high, low and open. 
As described above, a probe terminating apparatus according to the 
invention makes an in-circuit emulator small in size, simplified in 
construction and low in cost, because the in-circuit emulator is not 
required to have a space for the connection of a probe. 
Further, a probe terminating apparatus according to the invention induces 
no through-current at input gates and provides no influence on the 
reliability of a device of an evaluation microcomputer, etc. because 
terminals thereof are not required to be pulled up and down, thereby 
resulting in the change of electric characteristics. 
Still further, a probe terminating apparatus provides an in-circuit 
emulator, an evaluation microcomputer of which maintains to be equivalent 
to a microcomputer in a hardware to be evaluated in operation, because 
there is no necessity to include selectors and no consideration of signal 
propagation delay. 
Although the invention has been described with respect to specific 
embodiment for complete and clear disclosure, the appended claims are not 
to be thus limited but are to be construed as embodying all modification 
and alternative constructions that may be occur to one skilled in the art 
which fairly fall within the basic teaching herein set forth.