Portable electronic device with memory card unit having symmetrical terminals

In a device such as a personal computer having a memory card unit, terminals of a memory card are arranged symmetrically about power source terminals. When a memory card is inserted upside down into a memory card unit, the power source terminals are connected to a connector of a unit as in a normal operation, and other terminals are connected to identical types of terminals of the connector.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a portable electronic device such as a 
lap-top type personal computer or wordprocessor and, more particularly, to 
a device having a memory card unit. 
2. Description of the Related Art 
In recent years, portable electronic devices such as lap-top type personal 
computers and wordprocessors have been developed. Some devices have memory 
card units in addition to floppy disk drives (FDDs) as external memories. 
In such a device, a memory card unit is stored in a housing of the device, 
and a memory card used as a memory medium is inserted into the memory card 
unit. The memory card serves as an external memory. The memory card has a 
housing, and the housing has a card base consisting of a plastic 
plate-like member. A memory circuit consisting of integrated circuits 
(LSIs) is mounted on the card base. A plurality of terminals (i.e., a 
connector consisting of contact holes) electrically connected to the 
memory circuit is arranged at the distal end portion of the card base. 
The memory card unit has a box-like case for holding a memory card inserted 
into a card slot formed in a case unit constituting the housing of the 
device A connector corresponding to the plurality of terminals of the 
memory card is arranged in the box-like case. The connector is 
electrically connected to a predetermined circuit (external memory control 
circuit) on a printed circuit board to electrically connect the memory 
card to the printed circuit board. 
The memory card may be erroneously inserted upside down into the memory 
card unit through the card slot. In this case, i.e., in an abnormal 
insertion state, the plurality of terminals arranged at the distal end 
portion of the memory card are electrically connected to the connector of 
the unit. When the card is inserted upside down as described above, the 
terminals of the memory card are not connected to the predetermined 
terminals of the connector but to other terminals. For this reason, for 
example, an abnormal circuit is formed by connections of a high-voltage 
power source terminal of the connector and a data input/output (I/O) 
terminal of the memory card. In this abnormal circuit, an abnormal current 
flows in a memory circuit of the memory card or a circuit (e.g., a data 
processing circuit mounted on the printed circuit board) on the housing of 
the device, and one or both of the memory circuit and the circuit on the 
housing of the device may malfunction. 
In the device having the memory card unit as described above, the memory 
capacity of the memory card is smaller than that of a disk used in the 
FDD. For this reason, it is not so advantageous to use a memory card as an 
external memory medium in place of an FDD disk in practice. The memory 
cards have been used in application fields which require a small memory 
capacity and have limited operating conditions. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a portable electronic 
device such as a personal computer having a memory card unit, wherein a 
malfunction in one or both of a memory circuit of a memory card and each 
circuit of the device can be prevented even if the memory card is inserted 
upside down in the unit. 
It is another object of the present invention to provide a practical 
external memory system by using a memory card as an external memory medium 
having a relatively large capacity. 
A memory card according to the present invention comprises a card base 
constituting a housing of the card and mounted with a memory circuit, and 
connector means for connecting the memory circuit and an external device, 
the connector means being arranged on a flat surface of a distal end 
portion of the card case connected to the external device, and the 
connector means having a power source terminal connected to the memory 
circuit as a central terminal and symmetrical data input/output, address, 
and control signal terminals connected to the memory circuit. 
In this memory card, when the memory card is inserted upside down into the 
memory card unit, the terminals of the card are connected to the 
predetermined terminals of the connector of the external device. 
Therefore, even if the card is inserted upside down, connection of the 
card terminals to undesirable connector terminals, and formation of an 
abnormal circuit can be prevented. 
The device according to the present invention comprises: a control unit for 
executing operation control of the device; a case unit constituting a 
housing of the device and incorporating the control unit therein; a 
plurality of memory card units, arranged inside the case unit, for 
respectively storing a plurality of memory cards serving as external 
memory media of the device; and card interface means, respectively 
connected to the memory cards inserted in the memory card units, for 
interfacing the control unit with the memory cards. 
A large external memory system consisting of memory cards can be achieved 
by using a plurality of memory cards. Therefore, the memory capacity is 
not limited to the small capacity of one memory card, and an external 
memory system consisting of a practical large-capacity memory card system 
can be obtained. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The first embodiment of the present invention will be described with 
reference to the accompanying drawings. 
As shown in FIG. 1, a device of this embodiment is a lap-top type personal 
computer. This personal computer comprises a keyboard 2 and a flat panel 
display unit 3 and uses a case unit 1 constituting a device housing as a 
base. The keyboard 2 is mounted on the front surface portion of the case 
unit 1 and has a plurality of key switches. A handle 4 is mounted on the 
front surface portion of the case unit 1 and is used to carry the device 
housing. The display unit 3 comprises, e.g., an LCD (Liquid Crystal 
Display) panel 3a and is mounted on the rear surface portion of the case 
unit 1. The display unit 3 is mounted on the case unit 1 by a pivotal 
connecting member 5. When the computer is not used, a display panel 3a is 
pivoted about the connecting member 5 in a direction to come close to the 
keyboard 2, and the display unit 3 is closed at the front surface portion 
of the case unit 1. 
A memory card unit 6 and an FDD (Floppy Disk Drive) unit 7 are incorporated 
in a side surface portion of the case unit 1. The memory card unit 6 is 
located at the front surface portion of the case unit 1 under the keyboard 
2. 
The memory card unit 6 has a box-like case for receiving a memory card 8 
inserted from a card slot 6a formed in the side surface of the case unit 
1. 
The memory card 8 comprises a housing as a card base made of a plastic 
plate-like member. A memory circuit consisting of integrated circuits 
(LSIs) is mounted on the card base. The memory circuit comprises a ROM 
(Read-Only Memory) or an RWM (Read/Write Memory or so-called RAM). 
A connector 10 having a plurality of terminals (contact holes) is arranged 
at the distal end portion of the card base, as shown in FIG. 2. The 
connector 10 has high-voltage power source terminals 11 at its center and 
a plurality of other terminals symmetrical about the high-voltage power 
source terminals 11. The high-voltage power source terminals 11 are used 
to supply a power source voltage (e.g., 5 V) necessary for an operation of 
a memory circuit 12 mounted on the card 8. The power source is arranged 
inside the case unit 1 and is used as a power source for operating the 
computer as a whole. 
On one side with respect to the high-voltage power source terminals 11 as 
central terminals, a control signal terminal C2, data I/O terminals D0 to 
D7, address terminals A4 to A7, and ground terminals GND2 and GND3 are 
arranged. On the other side, a control signal terminal C1, data I/O 
terminals D8 to D15, address terminals A0 to A3, and ground terminals GND0 
and GND1 are arranged. These terminals are connected to the memory circuit 
12. 
The memory card unit 6 comprises a connector 20 corresponding to the 
connector 10 of the memory card 8. The connector 20 has connecting pins 
respectively corresponding to the terminals of the card 8 and is connected 
to the printed circuit board arranged inside the case unit 1. LSIs such as 
a central processing unit (CPU) and a card interface (C-IF) necessary for 
computer operations are mounted on the printed circuit board. 
As shown in FIG. 1, when the memory card 8 is inserted into the card slot 
6a of the card unit 1, the memory card 8 is stored in the memory card unit 
6. In the unit 6, the connector 10 of the memory card 8 is connected to 
the connector 20 of the unit 6. The memory card 8 is electrically 
connected to the printed circuit board arranged inside the case unit 1. 
Therefore, the CPU mounted on the printed circuit board can access the 
memory card 8 through the C-IF. That is, the CPU can use the memory card 8 
as an external memory unit as in the FDD. 
Assume that the memory card 8 is inserted upside down into the memory card 
unit 6 through the card slot 6a. In this erroneous insertion, the right 
(left) side of the connector 10 of the card 8 is connected to the left 
(right) side of the connector 20 of the unit 6 with respect to the 
high-voltage power source terminals 11 as central terminals. More 
specifically, in a normal connecting state, the control signal terminal 
C2, the data I/O terminals D0 to D7, the address terminals A4 to A7, and 
the ground terminals GND2 and GND3 are respectively connected to the 
control signal terminal C1, the data I/O terminals D8 to D15, the address 
terminals A0 to A3, and the ground terminals GND0 and GND1. Even if the 
connector 10 is reversely connected to the connector 20, since the 
high-voltage power source terminals 11 are located at the central portion 
of the connector 10, the terminals of the connector 10 can be connected to 
the proper pins of the connector 20, respectively, as in the normal 
insertion. Therefore, even if the connector 10 is inserted upside down, a 
high voltage from the power source in the case unit 1 will not be applied 
to any terminal (e.g., the data I/O terminal) except for the high-voltage 
power source terminals 11. 
The terminals except for the high-voltage power source terminals 11 are 
arranged symmetrically about the high-voltage power source terminals 11. 
Even if the terminals are reversely connected when the card 8 is inserted 
upside down, the terminals of the card 8 are connected to the 
corresponding types of terminal pins of the connector 20. 
Even if the memory card 8 according to the present invention is inserted 
upside down into the memory card unit 6, the high-voltage power source 
terminals 11 can be appropriately connected to the corresponding terminals 
of the connector 20. Unlike in the conventional case, an abnormal circuit 
is not formed upon connection of the data I/O terminals of the memory card 
to the high-voltage power source terminals of the connector 20 of the unit 
6 when the card is inserted upside down. Since formation of an abnormal 
circuit can be prevented as described above even if the memory card 8 is 
inserted upside down, an abnormal current is not supplied to, e.g., the 
memory circuit 12 or a CPU mounted on the printed circuit board of the 
computer, and a malfunction of one or both of the memory circuit 12 and 
the circuit on the printed circuit board can be prevented. 
In the first embodiment, the high-voltage power source terminals 11 are 
arranged at the central portion of the connector 10 of the memory card 8. 
However, the layout of the terminals is not limited to this. For example, 
the ground terminals may be arranged at the central portion in place of 
the high-voltage power source terminals 11. In this case, the high-voltage 
power source terminals 11 are located at any of the ground terminals GND0 
to GND3. As a matter of course, the positions of the control signal 
terminals C1 and C2, the data I/O terminals DO to D15, and the address 
terminals A0 to A7 are not limited to specific positions if they are 
symmetrical about the power source terminals (high-voltage power source 
terminals or the ground terminals). 
The second embodiment of the present invention will be described with 
reference to FIGS. 3 to 6. 
As shown in FIG. 3, a device of this embodiment is similar to the lap-top 
type personal computer as in the first embodiment. The personal computer 
comprises a memory card unit 6 arranged in the side surface portion of a 
case unit 1 and another memory card unit 16 arranged in the side surface 
portion of a display unit 3. The memory card unit 16 has a box-like case 
for storing a memory card 18 similar to a memory card 8. 
The memory card 18 comprises a housing consisting of a card base of, e.g., 
a plastic plate-like member as in the card 8. A memory circuit consisting 
of integrated circuits (LSIs) is mounted on the card base. The memory 
circuit comprises a ROM or RWM. When the memory card 18 is inserted into a 
card slot 18a formed in the side surface of the display unit 3, the card 
18 is connected to a connector (i.e., a connector 30 shown in FIG. 5) of 
the unit 16. The connector of the unit 16 is connected to a printed 
circuit board arranged inside the case unit 1. 
As shown in FIG. 4, the computer comprises a CPU 31 for executing data 
processing, a system bus 60, and a card interface (C-IF) 61 inside the 
case unit 1. The CPU 31 is connected to the C-IF 61 through the system bus 
60. The C-IF 61 is an interface for transferring data, address, and 
various control signals between the CPU 31 and the memory cards 8 and 18. 
The C-IF 61 is electrically connected to the connectors 20 and 30 arranged 
on the units 6 and 16 for respectively storing the memory cards 8 and 18. 
The CPU 31, the system bus 60, and the C-IF 61 are mounted on the printed 
circuit board. 
The computer further includes a ROM 32 for storing programs of the CPU 31, 
a RAM 33 for storing data necessary for data processing of the CPU 31, a 
direct memory access controller (DMAC) 34, a programmable interrupt 
controller (PIC) 35, a programmable interval timer (PIT) 36, a real-time 
clock (RTC) 37 having an independent operating battery, and a backup RAM 
(BK-RAM) 38 used as a data storage area for realizing a resuming function. 
Even if a commercial AC voltage (AC) is not applied from a main power 
source of the computer, a voltage from the backup power source VBK is 
supplied from a power source circuit 40 to the RAM 33 and the BK-RAM 38. 
The power source circuit 40 comprises a power control circuit (PC-CPU) 
which receives a DC voltage of a predetermined potential from an AC 
adapter 39 to supply an operating power to the respective components of 
the computer. The AC adapter 39 is a circuit for rectifying and smoothing 
an input AC power and outputting a DC voltage of a predetermined 
potential. The PC-CPU has a function of monitoring the entire internal 
power source of the computer. The power source circuit 40 receives DC 
voltages of a predetermined potential (i.e., the backup power sources VBK) 
from a rechargeable cartridge main battery (M-BATT) 41a and a rechargeable 
sub-battery (S-BATT) 41b incorporated in the case unit 1. A power source 
control interface (PS-IF) 49 connects the power source circuit 40 and the 
CPU 31 through the system bus 60. 
The computer further includes a printer controller (PRT-CONT) 42 serving as 
an interface for a printer (PRT) 51 as an external device, a universal 
asynchronous receiver transmitter (UART) 43 as an I/O interface with an 
external device, a keyboard controller (KBC) 44 as an interface for a 
keyboard (KB) 2, and a display controller (DISP-CONT) 45. The UART 43 is 
connected to an interface 52 complying with, e.g., the RS-232C Standards. 
The DISP-CONT 45 is a control circuit for controlling display operations 
of an LCD display panel 3a and a CRT display unit (CRT) 53. The DISP-CONT 
45 executes display operation control on the basis of the display data 
stored in a video RAM (VRAM) 46. The computer additionally includes a ROM 
47 for prestoring character pattern data required for displaying 
operations of the display unit and printing operations at the printer, a 
ROM 48 serving as a dictionary memory required for wordprocessor 
functions, and an extension connector 50 for connecting an extended 
memory. 
FIG. 5 is a block diagram showing the computer system configuration when a 
plurality of memory cards (8 and 18) are used in the computer of the 
second embodiment. 
The C-IF 61 includes card identification circuits 70 and 71 for identifying 
whether the memory cards 8 and 18 are set in the units 6 and 16, 
respectively. As shown in FIG. 5, the card identification circuit 70 is a 
circuit having a pull-up resistor 70a. When the memory card 8 is inserted 
into the unit 6 and is connected to the connector 20, an identification 
signal (a low-level voltage signal) ID1 is output from one terminal of the 
pull-up resistor 70a. Similarly, the card identification circuit 71 is a 
circuit including a pull-up resistor 71a. When the memory card 18 is 
inserted into the unit 16 and is connected to the connector 30, an 
identification signal (i.e., a low-level voltage signal) ID2 is output 
from one terminal of the pull-up resistor 71a to the CPU 31. The CPU 31 
identifies from the identification signal ID1 or ID2 from the C-FI 61 
whether the unit 6 or 16 is set in the memory card 8 or 18. 
The CPU performs identification processing for identifying the type of (ROM 
or RWM) of each memory circuit 12 or 22 set in the memory card 8 or 18 in 
accordance with a flow chart in FIG. 6. 
In step S1, the CPU 31 accesses the memory cards 8 and 18 through the C-IF 
61 and writes predetermined identification data at predetermined 
addresses. The CPU 31 then accesses the memory cards 8 and 18 through the 
C-IF 61 and reads out the identification data written in step S1 from the 
predetermined address (step S2). The CPU 31 compares the readout data with 
the written identification data to determine whether they coincide with 
each other (step S3). 
As shown in FIG. 5, assume that a ROM is incorporated in the memory card 8 
and that an RWM is mounted in the memory card 18. When the readout data 
coincides with the written identification data (i.e., YES in step S3), the 
CPU 31 identifies that an RWM is mounted in the memory card 18 (step S7). 
However, if the readout data does not coincide with the written 
identification data (i.e., NO in step S3), the CPU 31 identifies that a 
ROM is mounted in the memory card 8. In this case, since identification 
data cannot be written in the ROM, data read out from the predetermined 
address of the ROM does not coincide with the identification data. 
If NO in step S3, the CPU 31 reads out data from the predetermined address 
of the memory card 8 (step S4). The CPU 31 checks if the readout data 
coincides with the identification data prestored in the ROM (step S5). If 
the identification data is identified (i.e., YES in step S5), the CPU 31 
identifies that a ROM is mounted in the memory card 8 (step S6). However, 
when the identification data is not identified (i.e., No in step S5), the 
CPU 31 identifies that neither an RWM nor a ROM are mounted in the memory 
card 8 and that the memory card 8 is malfunctioning (step S8). 
The CPU 31 identifies types of memory circuits 12 and 22 of the plurality 
of memory cards 8 and 18 and executes memory control in accordance with 
the types of memory circuits. More specifically, since the memory card 8 
incorporates a ROM, the CPU 31 accesses the memory card 8 and executes 
read processing of various prestored data (or program). Since the memory 
card 18 incorporates an RWM, the CPU 31 uses the memory card 18 as a 
memory such as an extended RWM. When RWMs are respectively mounted in the 
memory cards 8 and 18, the CPU 31 can use the cards 8 and 18 as a single 
memory space. 
Since the plurality of memory cards 8 and 18 can be used as described 
above, the external memory can have a larger capacity than a configuration 
using a single memory card. Therefore, memory cards can be used as 
practical external memory media corresponding to an FDD disk. Although a 
single memory card has a small memory capacity and its application field 
is limited, this limitation can be eliminated by the present invention. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices, shown and described. 
Accordingly, various modifications may be made without departing from the 
spirit or scope of the general inventive concept as defined by the 
appended claims and their equivalents.