This invention relates generally to microcomputers, which term as used herein includes any device incorporating a CPU and a memory means.

Background to the invention

Microcomputers are commonly provided with ports having edge connectors enabling the attachment of peripheral devices, including additional memory blocks for example. In general, it is desirable for the microcomputer to be in a "shut down" condition when a peripheral is being attached or detached at the edge connector, for example to avoid crashes leading to irretrievable loss of data.

It is therefore known to fit a icroswitch adjacent the edge connector, which may for example be actuated by movement of a pivoted flap or the like, which microswitch when actuated initiates a general shut down of the computer. In this way it is intended that a peripheral is not attached and/or detached from the edge connector when there is risk of loss of data or other harmful effects.

However, a general shut down of the microcomputer is not achieved instantaneously on initiation thereof, and in spite of actuation of the microswitch, it remains necessary that the peripheral should not be attached and/or detached before the general shut down procedure has been completed. It is therefore known to provide an audible or other warning signal lasting for the duration of the general shut down procedure, but if this signal is

ignored, for example due to lack of understanding or impatience, data may be lost.

The invention

According to one aspect of the present invention, there is provided a microcomputer having a CPU, a memory means and an edge connector for attachment of a peripheral device, in combination with a peripheral device having an array of connectors for establishing an electrical interconnection between the microcomputer and the peripheral device at the contact pads of the edge connector, wherein the said array of connectors includes two connectors which are bridged so as to short circuit two contact pads of the edge connector prior to contact between any other connectors of the array and their corresponding edge connector contact pads, on insertion, or prior to contact between other connectors of the array and the edge connector pads being broken, on removal, and wherein the microcomputer is provided with circuit means responsive to short-circuiting of said two contact pads to initiate emergency shut down of the microcomputer.

An emergency shut down of the microcomputer is an instantaneous shut down analogous to that which may be arranged to take place in the event of a power failure for example. While not as satisfactory as a general shut down in safeguarding data, it avoids risk of damage and will usually save at least the more important data which might otherwise be rendered irretrievable.

Preferably, the invention as above described is used in conjunction with the known safety device incorporating a microswitch which initiates the preferred general shut

down procedure. If the general shut down procedure has been completed when the peripheral device is attached or detached, the subsequent initiation of an emergency shut down will be pre-empted, or it can be arranged that the circuitry in the microcomputer inhibits the emergency shut down instruction if a general shut down has already been completed.

The invention is especially applicable to a microcomputer of the CMOS type and especially a microcomputer of this type having one or more edge connectors enabling attachment of additional memory blocks, also of the CMOS type.

Especially but not exclusively in this type of computer, it is often important to arrange for the application of voltages to the additional memory block or other peripheral device to be sequenced.

According to another aspect of the invention, therefore, there is provided a peripheral device for a microcomputer having a CPU, a memory means and an edge connector for attachment of the peripheral device, which latter has an array of connectors corresponding to the edge connector contact pads, wherein the said connector array comprises connectors of differing effective lengths automatically to effect a required sequencing in the application or removal of voltages to the different circuits incorporated in the peripheral device when the latter is interconnected with or disconnected from the microcomputer.

A preferred arrangement of the invention utilises the two above-described aspects of the invention in combination. In this case, the Length oF the bridged section of the two

connectors producing emergency shut down is preferably such that the corresponding contact pads of the edge connector remain short circuited until all the other connector/contact pad interconnections have been sequentially established, whilst said bridged section terminates to open the said short circuit only after the last of said connector/contact pad interconnections has been completed, and vice versa.

In both aspects of the invention, it is preferably arranged for the connectors of the array on the peripheral to be of the same effective length mechanically. This is enabled by providing "dead" connector regions beyond the "active" portions thereof at which electrical interconnections are established. In this way it is avoided that the contact pads of the edge connector are undesirably abraded and/or worn when the peripheral device, e.g. additional memory block, is being attached or detached.

A preferred circuit provided in the microcomputer is a gate circuit from which regularly occurring interrupt

(INT) and non-maskable interrupt (NMI) signals are fed to the CPU. The NMI signal is generated when the two relevant contact pads of the edge connector, as hitherto described, are short-circuited. The NMI signal terminates when the said short circuit is removed.

Description of embodiment

A microcomputer and peripheral device therefor are exemplified in the following description, making reference to the accompanying drawings, in which:-

Figure 1 is a perspective view of a microcomputer, in particular showing the peripherals port and edge connectors thereof and associated safety device;

Figure 2a is a diagrammatic plan view of a micro¬ computer edge connector and a memory block circuit board adapted for connection to the microcomputer edge connector;

^p igure 2b is an end view of the edge connector assembly,

Figure 2c is an end view of one of the contact pads of the edge connector of Figure 2b; and

Figure 3 is a diagram of an emergency shut down control circuit within the microcomputer.

P.ef rring to Figure 1, a microcomputer 10 has edge connectors 12 at the rear of a port into which peripherals such as 15 can be inserted after opening a pivoted flap 14.

The latter controls a microswitch 17. In known manner, actuation of the microswitch when the flap is opened initiates a general shut down of the microcomputer. An audible warning signal is generated for the duration of the general shut down procedure. It can also readily be arranged that a general shut down is initiated by the microswitch when a peripheral device such as a memory block 15 is about to be detached from the edge connector. In neither case, however, is attachment or detachment of the peripheral device prevented while the general shut down procedure is still, taking place, if for one reason or

another the audible warning signal is ignored.

In accordance with the present invention, an instantaneous emergency shut down of the computer is effected if qeneraL shut down has not been completed prior to the act of attaching or detaching an additional memory block.

Referring to Figure 2a, reference 20 denotes the contact pads of the edge connector 14 of the microcomputer 10 and reference 22 denotes the connectors of an array thereof provided on a memory 24 (such as may be included within the peripheral 15 of Figure 1) adapted for interconnection with the microcomputer at said edge connector.

It can be seen that the connectors 22, whilst effectively being of the same length mechanically, have isolated or dead end regions 30 and active or live inner regions 32 which connect with the circuit board 24. The active regions 32 of the connectors are of differing appropriately pre-selected lengths, thereby to achieve a desired sequencing of the voltages applied to the memory block 24 when it is attached to the microcomputer, and likewise in reverse sequence on disconnection.

It can also be seen that three connectors, collectively referenced 40, are bridged together over their leading or outer end regions, two of said three connectors having the bridge continued over their inner regions. The full bridge over three connectors extends inwardly to a point just inwards of the ends of the shortest active regions 32 of the other connectors 22.

The effect of the fully bridged region of the three connectors is to short circuit two contact pads 50, 52 of

the contact pads 20 of the microcomputer edge connector 12 before any interconnections between the active regions of any of the other connectors 22 and corresponding contact pads 20 are established, when the memory block 24 is being attached, and likewise before any such interconnections are broken when the memory block is detached.

Figure 2b illustrates the edge connector housing 42 and shows how by using appropriately shaped contacts, conductive protrusions 44 cooperate to define a limited conductive region for attaching the conductive connectors 22 of the board 24. One such contact 46 is shown in more detail in Figure 2c.

Referring now to Figure 3, references 50, 52 again denote the two contact pads of the edge connector of the microcomputer which are temporarily short circuited during the act of attaching or detaching the memory block. Reference 54 denotes a third contact pad which provides a ground connection 56 and is interconnected with the contact pad 52. The three contact pads 50, 52, 54 correspond to the three connectors 40 of the memory block circuit board 24 hitherto identified with reference to Figure 2.

Immediately contact pads 50, 52 become short circuited, a gate array circuit 60, from which regularly occurring interrupt (INT) signals are fed to the CPU 62, is caused to supply a non-maskable interrupt (NMI) signal to the CPU, initiating an instantaneous emergency shut down of the microcomputer. The normal INT signal is inhibited for the duration that the contact pads 50, 52 are short circuited; this is to prevent the regular interrupts from reactivating the system for the duration of the short circuit.

It is thereby ensured that the microcomputer is in a shut down condition, as necessary to avoid crashing with loss of valuabl data and possible other damage, prior to the establishment or separation of any of the other connector/contact pad interconnections via which the memory block is operationally connected with the microcomputer. This safe condition is assured, even if the general shut down procedure described with reference to Figure 1 has not been completed.

It will be seen that on removal, the reverse procedure results and the bridged pair 40 again short the corresponding pair of contacts 50, 52 before the remaining contacts break from the other connectors of the assembly 22.

Various modifications of the above-described arrangement are possible within the scope of the invention hereinbefore defined. In this regard, it is again to be appreciated that the invention is applicable to microcomputing devices such as those employed in automatic machines, e.g. washing machines, in which an operational programme is determined by a programmed circuit block inserted into an edge connector provided on said microcomputing device.