Variable read latency on a serial memory bus
Systems and/or methods are provided that facilitate employing a variable read latency on a serial memory bus. In an aspect, a memory can utilize an undefined amount of time to obtain data from a memory array and prepare the data for transfer on the serial memory bus. The serial memory bus can be driven to a defined state. When data is ready for transfer, the memory can assert a start bit on the serial memory bus to notify a host prior to initiating the data transfer.
1. A method, comprising:
issuing, over a data bus, a read command and an address;
driving the data bus to a defined state, wherein the driving the data bus to the defined state comprises driving the data bus to the defined state during a handover time while a peripheral device drives the data bus to the defined state during the handover time;
releasing the data bus after a predetermined time comprising the handover time;
detecting a start indication on the data bus that is opposite to the defined state; and
capturing target data on the data bus.
2. The method of claim 1 , wherein the releasing the data bus after the predetermined time comprises releasing the data bus after at least one clock cycle that comprises the handover time.
3. The method of claim 2 , wherein the driving the data bus to the defined state comprises driving the data bus to the defined state by a host device during the handover time while a memory device drives the data bus to the defined state during the handover time.
4. The method of claim 1 , wherein the issuing comprises issuing the read command and the address to a memory device via the data bus using a host device.
5. The method of claim 1 , wherein the issuing comprises issuing the read command and the address to the peripheral device using a master device.
6. The method of claim 1 , wherein the driving the data bus to the defined state comprises driving the data bus to a low state.
7. The method of claim 1 , wherein the driving the data bus to the defined state comprises driving the data bus to a high state.
8. A method, comprising:
obtaining, over a data bus, a read command and an address;
obtaining data from a memory array associated with the address;
driving the data bus to a defined state after passage of a predetermined time period;
asserting a start indication on the data bus that is opposite to the defined state; and
transferring the data on the data bus.
9. The method of claim 8 , wherein the driving the data bus to the defined state comprises implementing a variable latency period during a read operation.
10. The method of claim 9 , further comprising accessing the memory array to obtain the data during the variable latency period.
11. The method of claim 8 , wherein the driving the data bus to the defined state comprises driving the data bus to the defined state after passage of a handover time.
12. The method of claim 8 , wherein the asserting the start indication comprises asserting at least a portion of a predetermined data pattern on the data bus.
13. The method of claim 12 , further comprising determining a capture time based on the predetermined data pattern.
14. The method of claim 12 , further comprising receiving the predetermined data pattern during a read operation.
15. The method of claim 12 , further comprising receiving the predetermined data pattern during an idle period.
16. The method of claim 12 , further comprising selecting a skew time based on the predetermined data pattern.