Overview

The AxiStreamBatcher firmware module takes incoming AXI stream and combines multiple sub-frames (packets) into a larger super-frame.

The batching protocol includes the some of the AXI-Stream's sideband data (TDEST and TUSER) information into the sub-frame tail.

The batching protocol is intended for use in firmware only and expects the debatching to be done in the software. Debatching not done in firmware due to the caching requirements at the sub-frame tail.

The batching protocol does not support partial frame interleaving for the sub-frames.  A sub-frame must be an entire AXI stream frame.

Together these features are very useful for sending high rate (>1MHz), small AXI-Stream frame into a CPU.

Details

Firmware Generics

NameDescription
MAX_NUMBER_SUB_FRAME_GMax. number of sub-frames in a super-frame
MAX_SUPER_FRAME_THRESHOLD_GSets the super-frame threshold (in units of bytes) to terminate the super-frame at the end of the current sub-frame
MAX_CLK_GAP_GSets the max. number of clocks cycle between sub-frame to terminate the current super-frame
AXIS_CONFIG_GDefines the AXI stream configuration and used to determine the AXI stream width from AXI_CONFIG_G.TDATA_BYTES_C

Super-Frame Header

The firmware batcher combines sub-frames in to larger super-frame. The super-frame has only 1 header per super-frame (no tail) as follows:

BitsNameDescription
3:0VERSIONVersion info. Should always be 0x1
7:4WIDTHlog2( (AXI stream bit width) /16-bits)
  • 0x0: 16-bit AXI stream
  • 0x1: 32-bit AXI stream
  • 0x2: 64-bit AXI stream
  • 0x3: 128-bit AXI stream
15:8SEQPacket sequence number of super-frame
OtherReservedAll reserved bits (undefined) bit set to zero

Notes

  • If TYPE = 16-bit AXI stream, then appended header is 2 bytes. 

  • If TYPE = 32-bit AXI stream, then appended header is 4 bytes.

  • If TYPE = 64-bit AXI stream, then appended header is 8 bytes. 

  • If TYPE = 128-bit AXI stream, then appended header is 16 bytes. 

  • If TYPE = 256-bit AXI stream, then appended header is 32 bytes.

  • If TYPE = 512-bit AXI stream, then appended header is 64 bytes.

Sub-Frame Tail

Each sub-frame within the super-frame is appended with a tail (no header) as follows:

BitsNameDescription
31:0SIZENumber of valid bytes in the sub-frame
39:32TDESTTDEST of AXI-Stream sub-frame
47:40TUSER_FIRSTTUSER of the AXI-Stream sub-frame
55:48TUSER_LASTTUSER of last transaction of the AXI-Stream sub-frame.
59:56WIDTHlog2( (AXI stream bit width) /16-bits)
  • 0x0: 16-bit AXI stream
  • 0x1: 32-bit AXI stream
  • 0x2: 64-bit AXI stream
  • 0x3: 128-bit AXI stream
OtherReservedAll reserved bits (undefined) bit set to zero

Notes

  • If TYPE = 16-bit AXI stream, then appended tail is 8 bytes. 

  • If TYPE = 32-bit AXI stream, then appended tail is 8 bytes.

  • If TYPE = 64-bit AXI stream, then appended tail is 8 bytes. 

  • If TYPE = 128-bit AXI stream, then appended tail is 16 bytes. 

  • If TYPE = 256-bit AXI stream, then appended header is 32 bytes.

  • If TYPE = 512-bit AXI stream, then appended header is 64 bytes.

Contact

Larry Ruckman

ruckman@slac.stanford.edu

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