Command-triggered on-die termination
An integrated circuit device transmits to a dynamic random access memory (DRAM) one or more commands that specify programming of a digital control value within the DRAM, the digital control value indicating a termination impedance that the DRAM is to couple to a data interface of the DRAM in response to receiving a write command and during reception of write data corresponding to the write command, and that the DRAM is to decouple from the data interface after reception of the write data corresponding to the write command. Thereafter, the integrated circuit device transmits to the DRAM a write command indicating that write data is to be sampled by a data interface of the DRAM during a first time interval and that cause the DRAM to couple the termination impedance to the data interface during the first time interval and decouple the termination impedance from the data interface after the first time interval.
1. A method of controlling a dynamic random access memory device (DRAM), the method comprising:
transmitting to the DRAM one or more commands that specify programming of a digital control value within the DRAM, the digital control value indicating a termination impedance that the DRAM is to couple to a data interface of the DRAM in response to receiving a write command and during reception of write data corresponding to the write command, and that the DRAM is to decouple from the data interface after reception of the write data corresponding to the write command; and
transmitting to the DRAM a write command indicating that write data is to be sampled by the data interface of the DRAM during a first time interval and, as a consequence of transmitting the one or more commands that specify programming of the digital control value, to cause the DRAM to couple the termination impedance to the data interface during the first time interval and decouple the termination impedance from the data interface after the first time interval.
2. The method of claim 1 further comprising transmitting the write data to the DRAM via a data path such that the write data arrives at the data interface of the DRAM during the first time interval.
3. The method of claim 1 wherein transmitting the one or more commands that specify programming of the digital control value within the DRAM comprises transmitting the digital control value to the DRAM.
4. The method of claim 1 wherein transmitting one or more commands that specify programming of the digital control value within the DRAM comprises transmitting one or more commands that specify storage of the digital control value within a configuration register of the DRAM.
5. The method of claim 1 wherein transmitting to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data and decouple from the data interface after reception of the write data comprises transmitting to the DRAM one or more commands that specify programming of first and second digital control values within the DRAM, the first digital control value indicating a first termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data corresponding to the write command and to decouple from the data interface after reception of the write data, and the second digital control indicating a second termination impedance that the DRAM is to couple to the data interface after reception of the write data.
6. The method of claim 5 wherein the first termination impedance that the DRAM is to couple to the data interface during reception of write data comprises a first subset of pull-up elements and pull-down elements within an output driver circuit of the DRAM and the second termination impedance that the DRAM is to couple to the data interface of the DRAM after reception of the write data comprises a second subset of pull-up elements and pull-down elements within the output driver circuit, wherein the second subset of pull-up elements and pull-down elements includes at least one pull-up element and/or pull-down element not included in the first subset of pull-up elements and pull-down elements.
7. The method of claim 1 wherein the data interface of the DRAM comprises a plurality of interconnects coupled to respective signal lines of an external data path, and wherein transmitting to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data corresponding to the write command comprises transmitting to the DRAM one or more commands that specify programming of a digital control value indicating a respective termination impedance that the DRAM is to couple to each interconnect of the data interface during reception of write data corresponding to the write command.
8. The method of claim 1 wherein transmitting to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data corresponding to the write command comprises transmitting to the DRAM one or more commands that specify one of a plurality of possible termination impedance values.
9. The method of claim 1 wherein transmitting to the DRAM a write command indicating that write data is to be sampled by the data interface of the DRAM comprises:
transmitting a command value to a command interface of the DRAM via a plurality of command signal lines; and
asserting a chip-select signal at a chip-select input of the DRAM via a chip-select signal line, the chip-select signal assertion indicating that the DRAM is to sample the command value at the command interface.
10. The method of claim 1 wherein transmitting to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM in response to reception of the write command comprises transmitting to the DRAM one or more commands that indicate a termination impedance that the DRAM is to couple to the data interface during an internal state of the DRAM effected by reception of the write command within the DRAM.
11. An integrated circuit device for controlling a dynamic random access memory device (DRAM), the integrated circuit device comprising:
a first signaling interface to transmit commands to the DRAM; and
control circuitry to transmit to the DRAM via the first signaling interface:
one or more commands that specify programming of a digital control value within the DRAM, the digital control value indicating a termination impedance that the DRAM is to couple to a data interface of the DRAM in response to receiving a write command and during reception of write data corresponding to the write command, and that the DRAM is to decouple from the data interface after reception of the write data corresponding to the write command; and
a write command indicating that write data is to be sampled by the data interface of the DRAM during a first time interval and, as a consequence of transmitting the one or more commands that specify programming of the digital control value, to cause the DRAM to couple the termination impedance to the data interface during the first time interval and decouple the termination impedance from the data interface after the first time interval.
12. The integrated circuit device of claim 11 further comprising a second signaling interface to transmit the write data to the DRAM via a data path such that the write data arrives at the data interface of the DRAM during the first time interval.
13. The integrated circuit device of claim 11 wherein the control circuitry to transmit the one or more commands that specify programming of the digital control value within the DRAM comprises circuitry to transmit the digital control value to the DRAM via the first signaling interface.
14. The integrated circuit device of claim 11 wherein the control circuitry to transmit the one or more commands that specify programming of the digital control value within the DRAM comprises circuitry to transmit, via the first signaling interface, one or more commands that specify storage of the digital control value within a configuration register of the DRAM.
15. The integrated circuit device of claim 11 wherein the control circuitry to transmit the one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data and decouple from the data interface after reception of the write data comprises circuitry to transmit, via the first signaling interface, one or more commands that specify programming of first and second digital control values within the DRAM, the first digital control value indicating a first termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data corresponding to the write command and to decouple from the data interface after reception of the write data, and the second digital control indicating a second termination impedance that the DRAM is to couple to the data interface after reception of the write data.
16. The integrated circuit device of claim 15 wherein the circuitry to transmit to the DRAM one or more commands that specify programming of first and second digital control values within the DRAM, comprises circuitry to transmit, via the first signaling interface, one or more commands that indicate, as the first and second digital control values, respective first and second subsets of pull-up elements and pull-down elements within an output driver circuit of the DRAM, wherein the second subset of pull-up elements and pull-down elements includes at least one pull-up element and/or pull-down element not included in the first subset of pull-up elements and pull-down elements.
17. The integrated circuit device of claim 11 wherein the data interface of the DRAM comprises a plurality of interconnects coupled to respective signal lines of an external data path, and wherein the control circuitry to transmit to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM during reception of write data corresponding to the write command comprises circuitry to transmit, via the first signaling interface, one or more commands that specify programming of a digital control value indicating a respective termination impedance that the DRAM is to couple to each interconnect of the data interface during reception of write data corresponding to the write command.
18. The integrated circuit device of claim 11 wherein the control circuitry to transmit to the DRAM a write command indicating that write data is to be sampled by the data interface of the DRAM comprises circuitry to transmit a command value to a command interface of the DRAM via a plurality of command signal lines, and to assert a chip-select signal at a chip-select input of the DRAM via a chip-select signal line, the chip-select signal assertion indicating that the DRAM is to sample the command value at the command interface.
19. The integrated circuit device of claim 11 wherein the control circuitry to transmit to the DRAM one or more commands that specify programming of the digital control value indicating the termination impedance that the DRAM is to couple to the data interface of the DRAM in response to reception of the write command comprises circuitry to transmit, via the first signaling interface, one or more commands that indicate a termination impedance that the DRAM is to couple to the data interface during an internal state of the DRAM effected by reception of the write command within the DRAM.
20. A machine-readable medium that stores data representative of an integrated-circuit memory controller comprising:
a first signaling interface to transmit commands to a dynamic random access memory device (DRAM); and
control circuitry to transmit to the DRAM via the first signaling interface:
one or more commands that specify programming of a digital control value within the DRAM, the digital control value indicating a termination impedance that the DRAM is to couple to a data interface of the DRAM in response to receiving a write command and during reception of write data corresponding to the write command, and that the DRAM is to decouple from the data interface after reception of the write data corresponding to the write command; and
a write command indicating that write data is to be sampled by a data interface of the DRAM during a first time interval and, as a consequence of transmitting to the DRAM the one or more commands that specify programming of the digital control value, to cause the DRAM to couple the termination impedance to the data interface during the first time interval and decouple the termination impedance from the data interface after the first time interval.