Transistor switch used to isolate bus devices and/or translate bus voltage levels
First Claim
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1. Simplified apparatus for transmitting data to and from a plurality of incompatible devices via a common bus, and for allowing each of the plurality of incompatible devices to receive data transmitted to or from another of the plurality of incompatible devices, the apparatus comprising:
- a) a shared data bus;
b) a plurality of devices connected to the shared data bus, the plurality of devices comprising at least first and second devices;
c) a number of field effect transistors having source and drain terminals, wherein each of the number of field effect transistors bridges a single line of the shared data bus view said source and drain terminals, at a point in between points where the first and second devices connect to the shared data bus; and
d) at least one voltage regulator, each of the at least one voltage regulators being connected to one or more gate terminals of the number of field effect transistors.
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Abstract
A plurality of MOSFET switches, one per bus line, are used to solve the problem of interfacing between two incompatible devices via a single shared bus. The MOSFET switches used are simple, inexpensive, and very fast. The switches perform two primary functions: 1) isolation of two bus sections (possibly for loading reasons); and 2) translation of incompatible voltages transmitted over the bus.
42 Citations
17 Claims
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1. Simplified apparatus for transmitting data to and from a plurality of incompatible devices via a common bus, and for allowing each of the plurality of incompatible devices to receive data transmitted to or from another of the plurality of incompatible devices, the apparatus comprising:
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a) a shared data bus; b) a plurality of devices connected to the shared data bus, the plurality of devices comprising at least first and second devices; c) a number of field effect transistors having source and drain terminals, wherein each of the number of field effect transistors bridges a single line of the shared data bus view said source and drain terminals, at a point in between points where the first and second devices connect to the shared data bus; and d) at least one voltage regulator, each of the at least one voltage regulators being connected to one or more gate terminals of the number of field effect transistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of selectively isolating a high speed access memory from a heavily loaded memory, the method comprising the steps of:
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a) connecting the high speed access and heavily loaded memories to a common bus; b) bridging each line of the common bus with a field effect transistor switch, at a point in between points where the high speed access memory and heavily loaded memory are connected to the common bus, each bridge being formed via connections to the source and drain terminals of a field effect transistor; and c) when desiring to isolate the high speed access memory from the heavily loaded memory, opening each field effect transistor switch by applying an appropriate voltage to the gate terminal.
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14. A method of updating a cache memory while reading a main memory, the method comprising the steps of:
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a) connecting the cache memory and main memory to a common bus; b) bridging each line of the common bus with a field effect transistor switch, at a point in between points where the cache memory and main memory are connected to the common bus, each bridge being formed via connections to the source and drain terminals of a field effect transistor; c) when desiring to update the cache memory while reading the main memory; i) closing each field effect transistor switch by applying an appropriate voltage to the gate terminal; and ii) substantially simultaneously; A) disabling output buffers of the cache memory; B) enabling input buffers of the cache memory; and C) driving lines of the common bus with data stored in main memory. - View Dependent Claims (15)
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16. A method of transmitting data across a common bus connected to a plurality of devices, the method comprising the steps of:
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a) bridging each line of the common bus with a field effect transistor switch, at a point in between points where first and second devices are connected to the common bus, each bridge being formed via connections to the source and drain terminals of a field effect transistor; b) before the first device transmits data across the common bus, opening each field effect transistor switch by applying a first voltage to the gate terminal; and c) before the second device transmits data across the common bus, closing each field effect transistor switch by applying a second voltage to said gate terminal. - View Dependent Claims (17)
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Specification