US 6,191,634 B1Granted

Data communications system and interface apparatus for data communications

AssigneeCasio Computer Co., Ltd.

InventorHiroyasu Haseyama

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Abstract

A data communication interface between a high-power device and a low-power device enabling wherein a cable having connectors at its both ends connects the high-power device and the low-power device; and the low-power device has its own incorporated level conversion circuit and drives same with a voltage which is supplied as a source voltage for the low-power device. The circuit receives a data signal at voltage levels compatible with the high-power device. The circuit converts the received signal into a data signal which is acceptable by the low-power device. The circuit receives from the low-power device a data signal at voltage levels compatible with the low-power device, and also converts the received signal into a signal which is acceptable by the high-power device. The level conversion circuit needs no element, such as a zener diode, for lowering (clamping) a voltage because the circuit is powered by the low-power device. The circuit can be miniaturized by thus excluding such a clamp element, and the connectors are also miniaturized because the low-power device incorporates the level conversion circuit therein.

Claims4

Dependent claims

A data communications interface apparatus comprising a signal level conversion circuit interconverting signal levels of a high-power device and a low-power device in order to enable two-way data communication to be performed between said high-power device and said low-power device when said high-power device and said low-power device are connected to each other via a cable;

wherein said signal level conversion circuit comprises:
a low-to-high power level conversion circuit which receives a signal output from the low-power device and converts a level of the received signal so as to match with an input signal level useable by the high-power device;
and
wherein said low-to-high power level conversion circuit comprises:
a low power source obtaining line to which a power source is supplied from the low-power device;
and
a first switching device which is switched on when the signal received from said low-power device has a first level, and which is switched off when the signal received from said low-power device has a second level different from the first level;
said low-to-high power level conversion circuit controlling a current obtained from said low-power source obtaining line to flow to the high-power device via said first switching device while said first switching device is switched on, thereby applying to said high-power device a signal having a voltage level which is suitable for use by said high-power device;
and
said low-to-high power level conversion circuit opening connection between said first switching device and said high-power device while said first switching device is switched off, and supplying to said high-power device a voltage which is pulled down so as to match with a negative voltage level which is receivable and useable by said high-power device.

7 more elements

A data communications interface system comprising a data communications interface apparatus including a cable for enabling data communications to be performed between a high-power device and a low-power device, and a signal level conversion circuit which interconverts signal levels of said high-power device and said low-power device;

wherein said signal level conversion circuit comprises:
a low-to-high power level conversion circuit which receives a signal output from the low-power device and converts a level of the received signal so as to match with an input signal level of the high-power device;
and
a high-to-low power level conversion circuit which receives a signal output from the high-power device and converts a level of the received signal so as to match with an input signal level of the low-power device;
wherein said low-to-high power level conversion circuit comprises:
a low power source obtaining line to which a power source output from the low-power device is supplied;
and
a first switching device which is switched on when the signal received from said low-power device has a low level, and which is switched off when the signal received from said low-power device has a high level;
said low-to-high power level conversion circuit controlling a current obtained from said low-power source obtaining line to flow via said first switching device while said first switching device is switched on, thereby applying to said high-power device a signal having a voltage level which is suitable for said low-power device, as a signal having a high level;
and
said low-to-high power level conversion circuit opening a connection between said first switching device and the high-power device while said first switching device is switched off, and supplies to the high-power device a voltage which is pulled down so as to match with a negative voltage level which is receivable by the high-power device;
and
wherein said high-to-low power level conversion circuit comprises:
a second switching device which is switched on when the signal received from said high-power device has a high level, and which is turned off when the signal received from said high-power device has a low level;
said high-to-low power level conversion circuit supplying a signal having a ground level from said high-power device to said low-power device via said second switching device, while said second switching device is switched on, as a signal having a low level which said low-power device can receive;
and
said high-to-low power level conversion circuit opening connection between said second switching device and said low-power device while said second switching device is switched off, and supplying to said low-power device a voltage which is pulled up so as to match with a voltage level of said low-power device.

14 more elements

Dependencies are inferred from the claim text.