Dynamic memory controller for single-chip microprocessor
First Claim
1. In combination, dynamic memory means for storing one bit of each of a plurality of data words in each cell along one of a plurality of rows each containing a multiplicity of said cells, said dynamic memory means requiring periodic refreshment, within a maximum time interval, of at least one cell along each of said rows, and including a plurality N of address inputs for designating at least the row of said memory means to be addressed;
- single-chip microprocessor means internally containing at least a cpu and an internal memory, for utilization of the data stored into said dynamic memory means, which is external to said microprocessor means, and including means for providing a periodic clock signal timing means for causing a refresh sequence for the external memory means to be initiated at a time not longer than the maximum time interval after a previous refreah sequence has been initiated;
means for periodically providing a single external memory enable signal during each of a sequential multiplicity of operational cycles of said miroprocessor means;
at least two output ports of N bit-lines each; and
refresh-addressing means for presenting a refresh row designation data to at least one designated one of said output ports responsive to an initiation of a refresh sequence by said timing means; and
address means, activated directly and solely by said clock signal and said single external memory enable signal and responsive to said timing means initiating said refresh sequence, for sequentially addressing at least one cell along each of said plurality of memory means rows to refresh the information stored in all cells along that memory row having the cell then being addressed;
said address means including;
multiplexing means for selectively connecting each of the N bit-lines of said at least one designated one of the microprocessor means output ports to the associated one of the row-designating N inputs of said dynamic memory means, with the designation of the one output port of said microprocessor means then connected being responsive to different states of a selection signal; and
logic means for providing the selection signal state responsive only to receipt of both said clock signal and said external memory enable signal from said microprocessor means, including a first flip-flop logic element having a clock input receiving said clock signal, a data input receiving said external memory enable signal, and an output providing said selection signal and having an output state determined by both the state of the data input signal and the occurrence of a first pulse of said clock signal exit clock input; and
said memory means accepts thr ow designation data at said address inputs responsive to a row-address strobe signal generated by a change in said external memory enable signal prior to another pulse of said clock signal, occurring after said first clock signal pulse.
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Abstract
A controller for interfacing a single-chip microcomputer with external dynamic random-access memory, includes a subcircuit for generating a column-address strobe at a time after a row-address strobe is generated, and also includes a multiplexing subcircuit for providing the proper 8-bit portion of a 16-bit address output from the microprocessor to the 8-bit dynamic memory inputs, prior to receipt of the associated row-address or column-address strobe. The microprocessor utilizes the strobe-generation and multiplexing subcircuits to burst-refresh the dynamic memory, in one presently preferred embodiment. In another presently preferred embodiment, lines from an additional microprocessor output port are utilized with a resettable binary counter and a multiplicity of buffers, to count through the range of row addresses in cyclic fashion, with each address being incremented after the previously-addressed row of memory cells has been refreshed.
116 Citations
15 Claims
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1. In combination, dynamic memory means for storing one bit of each of a plurality of data words in each cell along one of a plurality of rows each containing a multiplicity of said cells, said dynamic memory means requiring periodic refreshment, within a maximum time interval, of at least one cell along each of said rows, and including a plurality N of address inputs for designating at least the row of said memory means to be addressed;
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single-chip microprocessor means internally containing at least a cpu and an internal memory, for utilization of the data stored into said dynamic memory means, which is external to said microprocessor means, and including means for providing a periodic clock signal timing means for causing a refresh sequence for the external memory means to be initiated at a time not longer than the maximum time interval after a previous refreah sequence has been initiated;
means for periodically providing a single external memory enable signal during each of a sequential multiplicity of operational cycles of said miroprocessor means;
at least two output ports of N bit-lines each; and
refresh-addressing means for presenting a refresh row designation data to at least one designated one of said output ports responsive to an initiation of a refresh sequence by said timing means; andaddress means, activated directly and solely by said clock signal and said single external memory enable signal and responsive to said timing means initiating said refresh sequence, for sequentially addressing at least one cell along each of said plurality of memory means rows to refresh the information stored in all cells along that memory row having the cell then being addressed;
said address means including;
multiplexing means for selectively connecting each of the N bit-lines of said at least one designated one of the microprocessor means output ports to the associated one of the row-designating N inputs of said dynamic memory means, with the designation of the one output port of said microprocessor means then connected being responsive to different states of a selection signal; and
logic means for providing the selection signal state responsive only to receipt of both said clock signal and said external memory enable signal from said microprocessor means, including a first flip-flop logic element having a clock input receiving said clock signal, a data input receiving said external memory enable signal, and an output providing said selection signal and having an output state determined by both the state of the data input signal and the occurrence of a first pulse of said clock signal exit clock input; and
said memory means accepts thr ow designation data at said address inputs responsive to a row-address strobe signal generated by a change in said external memory enable signal prior to another pulse of said clock signal, occurring after said first clock signal pulse. - View Dependent Claims (2, 3)
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4. In combination, dynamic memory means for storing one bit of each of a plurality of data words in each cell along one of a plurality of rows each containing a multiplicity of said cells, said dynamic memory means requiring periodic refreshment, within a maximum time interval, of at least one cell along each of said rows;
- and including a plurality N or address inputs for receiving data, responsive to a row-address strobe signal, for designating at least the row of said memory means to be addressed;
single-chip microprocessor means internally containing at least a CPU and an internal memory, for utilization of the data stored in said dynamic memory means, which is external to said microprocessor means, and including means for providing a periodic clock signal;
timing means for causing a refresh sequence for the external memory means to be initiated at a time not longer than the maximum time interval after a previous refresh sequence has been initiated;
means for periodically providing a single external memory enable signal during each of a sequential multiplicity of operational cycles of said microprocessor means; and
means for providing a clearing signal which is normally enabled and is temporarily disabled, for the duration of a refresh sequence, responsive to said timing means determining that a refresh sequence is required; andaddress means, activated directly and solely by said clock signal and said single external memory enable signal and responsive to said timing means initiating said refresh sequence, for sequentially addressing at least one cell along each of said plurality of memory means rows to refresh the information stored in all cells along that memory row having the cell then being addressed, and including;
a first flip-flip logic element having a clock input receiving said clock signal, a data input receiving said external memory enable signal, and an output having an output state determined by both the state of the data input signal and occurrence of a first pulse of said clock signal at said clock input;
means for generating said row-address strobe signal responsive to a change in said external memory enable signal prior to another pulse of said clock signal, occurring after said first clock signal pulse;
a second flip-flop logic element having a clock input receiving said closk signal, a data input receiving the inversion of the output signal of said first flip-flop logic element, and an output providing a column-address strobe signal responsive to the state of said data input when a different pulse of said clock signal occurs at said second flip-flop logic element clock input at a selected time after the occurrence of said another clock signal pulse;
counter means for sequentially counting, with one count change being responsive to each occurrence of said column-address strobe signal, through a plurality of different ouput states, equal at least to the number of the plurality of row addresses, said counter means being cleared to a lowest count responsive to the enablement of said clearing signal and enabled to count responsive to the disablement of said clearing signal; and
means for providing the output count of said counter means to the plurality of memory means address inputs for designating the row of said memory means to be addressed. - View Dependent Claims (5, 6, 7, 8)
- and including a plurality N or address inputs for receiving data, responsive to a row-address strobe signal, for designating at least the row of said memory means to be addressed;
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9. A controller for interfacing external dynamic memory means for storing each bit of a plurality of data words in one of a plurality of cells along each of a plurality of rows each containing a multiplicity of said cells, and having a plurality N of address input lines for designating at least the memory means row responsive to a row-address strobe signal, and a microprocessor, having a CPU and an internal memory and having at least two output ports, each containing at least a plurality N of bit-lines at which at least external memory addressing data is provided, with the microprocessor providing only a periodic clock signal and an external memory enable signal, along with said at least external memory addressing data, to said controller;
- said controller comprising;
multiplexing means for selectively connecting each of N selected bit-lines of a designated one of the microprocessor output ports to a predetermined on of the N address inputs of the external dynamic memory means;
that one of the plurality of microprocessor means output ports then being connected to said memory means being designated responsive to a selected one of a plurality of different states of a selection signal; andlogic means for providing the selection signal state responsive to receipt of both said clock signal and said external memory enable signal, and including;
a first flip-flop logic element having a data input receiving said external memory enable signal, a clock input receiving said clock signal and an output providing said selection signal and having each of the plurality of different states determined by both the state of the data input signal and the occurrence of a first pulse of said clock signal at said clock input, and means for providing said row-address strobe signal responsive only to a change in the external memory enable signal prior to another pulse of said clock signal occurring after said first clock signal pulse. - View Dependent Claims (10, 11, 12, 13, 14, 15)
- said controller comprising;
Specification