Latency-optimized physical coding sublayer
Method and apparatus for reducing latency in a networking application comprises receiving data at a physical coding sublayer (PCS) from a media access control (MAC) sublayer, wherein the MAC sublayer utilizes a first clock domain operating at a first clock frequency. The method further comprises performing one or more functions in the PCS on the data in the first clock domain. The method also includes transmitting the data on one or more physical medium attachment (PMA) lanes, wherein the one or more PMA lanes utilize a second clock domain operating at a second clock frequency, wherein the first clock frequency and the second clock frequency have a fixed ratio. The method also comprises performing one or more functions in the PCS on the data in the second clock domain.
1. A system, comprising:
a media access control (MAC) sublayer configured to send data to a physical coding sublayer (PCS) utilizing a first clock domain operating at a first clock frequency; and
one or more physical medium attachment (PMA) lanes configured to transmit data utilizing a second clock domain operating at a second clock frequency, wherein the first clock frequency and the second clock frequency have a fixed ratio, wherein the fixed ratio between the first clock frequency and the second clock frequency is 32:33, and wherein data is transmitted from the first clock domain to the second clock domain without buffering the data.
2. The system of claim 1 , further comprising:
a phase-locked loop (PLL) configured to generate the first clock frequency and the second clock frequency.
3. The system of claim 1 , further comprising:
two or more plesiochronous first-in, first-outs (FIFOs), each FIFO configured to receive data from a separate PMA lane in the second clock domain and further configured to synchronize the data in the PMA lanes.
4. The system of claim 1 , further comprising:
an asynchronous output FIFO configured to receive data from the second clock domain and output data in the first clock domain.
5. A computer program product for reducing latency, the computer program product comprising:
a computer-readable storage medium having computer-readable program code embodied therewith, the computer-readable program code comprising:
computer-readable program code configured to receive data at a physical coding sublayer (PCS) from a media access control (MAC) sublayer, wherein the MAC sublayer utilizes a first clock domain operating at a first clock frequency;
computer-readable program code configured to perform one or more functions in the PCS on the data in the first clock domain;
computer-readable program code configured to transmit the data on one or more physical medium attachment (PMA) lanes after performing one or more functions in the PCS, wherein the one or more PMA lanes utilize a second clock domain operating at a second clock frequency, wherein the first clock frequency and the second clock frequency have a fixed ratio, wherein the fixed ratio between the first clock frequency and the second clock frequency is 32:33, and wherein the data is transmitted from the first clock domain to the second clock domain without buffering the data; and
computer-readable program code configured to perform one or more functions in the PCS on the data in the second clock domain.
6. The computer program product of claim 5 , further comprising:
computer-readable program code configured to transmit the data to an asynchronous output first-in, first-out (FIFO) located in the first clock domain after performing one or more functions on the data in the second clock domain.
7. The computer program product of claim 5 , further comprising:
computer-readable program code configured to transmit data from a transmit side of the PCS to a receive side of the PCS via one or more PMA lanes.
8. The computer program product of claim 7 , wherein the data is received from the one or more PMA lanes in one or more plesiochronous input FIFOs on the receive side of the PCS.