Source-synchronous data transmission with non-uniform interface topology
A source-synchronous system is provided in which a non-uniform interface may exist in a data source endpoint as well as in a data sink endpoint.
1. A source-synchronous data sink endpoint integrated circuit, comprising:
a first on-die capacitive termination within the integrated circuit for a data strobe channel for receiving a data strobe from a second integrated circuit, the first capacitive termination having an impedance mismatched to a resistive impedance for the data strobe channel;
an on-die resistive termination within the integrated circuit for a data channel for receiving a data signal from the second integrated circuit, the resistive termination having an impedance matching a resistive impedance for the data channel; and
a first register configured to register the data signal received on the resistive termination, the first register having a clock input configured to be clocked by the data strobe received on the first capacitive termination.
2. The source-synchronous data sink endpoint integrated circuit of claim 1 , wherein the data strobe channel is a true data strobe channel, the data sink endpoint further comprising a second capacitive termination for a complement data strobe channel, the second capacitive termination having an impedance mismatched to a resistive impedance for the complement data strobe channel.
3. The source-synchronous data sink endpoint integrated circuit of claim 2 , further comprising a second register configured to register data received on the resistive termination, the second register having a clock input configured to be clocked by a complement data strobe received on the second capacitive termination.
4. The source-synchronous data sink endpoint integrated circuit of claim 2 , wherein the first capacitive termination is coupled to the second capacitive termination through a coupling resistor.
5. The source-synchronous data sink endpoint integrated circuit of claim 1 , wherein the source-synchronous data sink endpoint comprises a dynamic random access memory (DRAM) integrated circuit.
6. The source-synchronous data sink endpoint integrated circuit of claim 1 , wherein the first capacitive termination is coupled to a power supply voltage node through a weak pull-up resistor.
7. The source-synchronous data sink endpoint integrated circuit of claim 1 , wherein the resistive termination comprises a parallel combination of a resistor and a capacitor.
8. The source-synchronous endpoint integrated circuit of claim 1 , further comprising a second capacitive termination for a clock channel, the second capacitive termination having an impedance that is mismatched with regard to a resistive impedance of the clock channel.
9. A method, comprising:
in a first integrated circuit, receiving at a first capacitive termination a first data strobe transmitted over a first data strobe channel from a second integrated circuit;
in the first integrated circuit, receiving at a resistive termination a data signal transmitted over a data channel from the second integrated circuit; and
in the first integrated circuit, registering the data signal responsive to a clock edge in the received first data strobe.
10. The method of claim 9 , further comprising receiving at a second capacitive termination a second data strobe transmitted over a second data strobe channel.
11. The method of claim 10 , further comprising registering the data signal responsive to a clock edge in the received second data strobe.
12. The method of claim 9 , further comprising receiving at a second capacitive termination a clock signal.