Multi-valued on-die termination
An integrated circuit memory device stores a plurality of digital values that specify respective termination impedances. The memory device switchably couples respective sets of load elements to a data input/output (I/O) to apply the termination impedances specified by the digital values, including, applying a first termination impedance to the data I/O during an idle state of the memory device, applying a first one of two non-equal termination impedances to the data I/O while the memory device receives write data in a memory write operation and applying a second one of the two non-equal termination impedances to the data I/O while another memory device receives write data in a memory write operation. When outputting read data via the data I/O in a memory read operation, the memory device switchably couples to the data I/O at least a portion of the load elements included in the sets of load elements.
1. A method of operation within an integrated circuit memory device, the method comprising:
storing a plurality of digital values that specify respective termination impedances;
switchably coupling sets of load elements to a data input/output (I/O) to apply termination impedances specified by the digital values, wherein switchably coupling the sets of load elements to the data I/O includes:
applying a first termination impedance to the data I/O during an idle state of the memory device, and
applying one of two non-equal termination impedances to the data I/O, including applying a first one of the non-equal termination impedances to the data I/O while the memory device receives write data in a memory write operation and applying a second one of the non-equal termination impedances to the data I/O while another memory device receives write data in a memory write operation; and
outputting read data via the data I/O in a memory read operation, wherein outputting read data includes switchably coupling to the data I/O at least a portion of the load elements included in the sets of load elements.
2. The method of claim 1 wherein switchably coupling at least one of the sets of load elements to the data I/O comprises enabling, as a group, a plurality of transistor switches to couple the at least one of the sets of load elements to the data I/O to effect a corresponding one of the termination impedances.
3. The method of claim 1 wherein the first termination impedance and the second one of the non-equal termination impedances have matching impedance values.
4. The method of claim 1 further comprising executing an activate operation or a pre-charge operation within the integrated circuit memory device while applying the second one of the non-equal termination impedances and while the other memory device receives write data.
5. The method of claim 1 wherein the first and second non-equal termination impedances have respective impedance values that are unequal to one another and wherein at least one of the impedance values of the first and second non-equal termination impedances is also unequal to the impedance value of the first termination impedance.
6. The method of claim 1 wherein the respective sets of load elements comprise a first set of load elements corresponding to the first termination impedance and a second set of load elements corresponding to the first one of the non-equal termination impedances, wherein at least one load element is included in both the first set of load elements and the second set of load elements.
7. The method of claim 1 wherein at least one load element of the respective sets of load elements is included within an output signal driver, the at least one load element being switchably coupled between the data I/O and a pull-up voltage node or pull-down voltage node when the output signal driver is enabled to drive a signal via the data I/O.
8. The method of claim 1 wherein at least one of the termination impedances specified by the digital values comprises pull-up elements and pull-down elements within an output driver circuit of the integrated circuit memory device.
9. The method of claim 8 further comprising switchably coupling the pull-up elements between the data I/O and a pull-up voltage node to transmit a data signal having a first state, and switchably coupling the pull-down elements between the data I/O and a pull-down voltage node to transmit a data signal having a second state.
10. The method of claim 1 wherein switchably coupling the respective sets of load elements to the data I/O is performed in accordance with operating states of the memory device, and wherein switchably coupling the respective sets of load elements to the data I/O is controlled based on the state of a termination control signal and memory commands received from a memory control component, the operating states of the memory device including the idle state, a memory write state during which the memory device receives the write data, a memory read state during which the memory device transmits the read data, an activate state which precedes a memory read or memory write operation, and a precharge state which follows a memory read or memory write operation.
11. An integrated circuit memory device comprising:
programmable storage circuitry to store a plurality of digital values that specify respective termination impedances;
a data input/output (I/O) to be coupled to an external data signaling line; and
termination circuitry to switchably couple respective sets of load elements to the data I/O to apply the termination impedances specified by the digital values, the termination circuitry to:
apply a first termination impedance to the data I/O during an idle state of the memory device,
apply one of two non-equal termination impedances to the data I/O, including applying a first one of the non-equal termination impedances to the data I/O while the memory device receives write data in a memory write operation and applying a second one of the non-equal termination impedances to the data I/O while another memory device receives write data in a memory write operation, and
output read data via the data I/O in a memory read operation, including switchably coupling to the data I/O at least a portion of the load elements included in the sets of load elements.
12. The integrated circuit memory device of claim 11 wherein the termination circuitry comprises circuitry to enable, as a group, a plurality of transistor switches to couple at least one of the sets of load elements to the data I/O to effect a corresponding one of the termination impedances.
13. The integrated circuit memory device of claim 11 wherein the first termination impedance and the second one of the non-equal termination impedances have matching impedance values.
14. The integrated circuit memory device of claim 11 further comprising control circuitry to execute an activate operation or a pre-charge operation within the integrated circuit memory device while the termination circuitry applies the second one of the non-equal termination impedances and while the other memory device receives write data.
15. The integrated circuit memory device of claim 11 wherein the first and second non-equal termination impedances have respective impedance values that are unequal to one another and wherein at least one of the impedance values of the first and second non-equal termination impedances is also unequal to the impedance value of the first termination impedance.
16. The integrated circuit memory device of claim 11 wherein the respective sets of load elements comprise a first set of load elements corresponding to the first termination impedance and a second set of load elements corresponding to the first one of the non-equal termination impedances, wherein at least one load element is included in both the first set of load elements and the second set of load elements.
17. The integrated circuit memory device of claim 11 further comprising an output signal driver to transmit the read data via the data I/O, and wherein at least one load element of the respective sets of load elements is included within the output signal driver, the at least one load element being switchably coupled between the data I/O and a pull-up voltage node or pull-down voltage node when the output signal driver is enabled to drive a signal via the data I/O.
18. The integrated circuit memory device of claim 11 further comprising an output driver circuit to transmit the read data via the data I/O and wherein at least one of the termination impedances specified by the digital values comprises pull-up elements and pull-down elements within the output driver circuit.
19. The integrated circuit memory device of claim 18 wherein the termination circuitry to switchably couple respective sets of load elements to the data I/O comprises circuitry to (i) switchably couple the pull-up elements between the data I/O and a pull-up voltage node to transmit a data signal having a first state, and (ii) switchably couple the pull-down elements between the data I/O and a pull-down voltage node to transmit a data signal having a second state.
20. A dynamic random access memory (DRAM) device comprising:
a data input/output (I/O); and
termination circuitry to switchably couple termination impedances to the data I/O, the termination circuitry including circuitry to:
switchably couple to the data input/output (I/O) a termination impedance that corresponds to an idle state of the DRAM;
switchably couple to the data I/O each of two non-equal termination impedances that correspond to respective non-idle states of the DRAM, at least one of the non-idle states being a write state in which a write data signal is sampled by the DRAM at the data I/O; and
switchably couple to the data I/O load elements included in the termination impedances during a read state of the DRAM to effect transmission of a read data signal via the data I/O.