High Bandwidth Memory (HBM2E) Interface Intel Agilex® 7 M-Series FPGA IP User Guide

ID 773264
Date 12/04/2023
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5.2.4. AXI4 Interface Signals

The AXI interface to the HBM2E controller follows the Amba AXI4 protocol specification. Each AXI interface serves the read and write operations for one pseudo channel, and is connected to a NoC target. Your design should issue AXI commands to the HBM2E controller(s) via one or more instances of the NoC Initiator Intel FPGA IP. You can configure the hard memory NoC so that your design can use a single AXI interface to access any or all of the pseudo-channels. The hard memory NoC can also be configured to suit designs that use multiple AXI interfaces to initiate NoC commands to a common set of pseudo-channels.

AXI Interface Signals

The hard memory NoC uses the upper 14 bits of AXI addresses to direct commands to the 16 HBM pseudo-channels.

Each AXI interface consists of five subchannels:

  • Write Address Channel –AXI write commands, specifying the target address, transfer size, and associated information.
  • Write Data Channel – AXI write data provided by the core logic corresponding to the write address.
  • Write Response Channel – Response from the HBM2E controller indicating whether or not each write has been accepted.
  • Read Address Channel – AXI read commands, specifying the target address, transfer size, and associated information.
  • Read Data Channel – AXI read data provided from the corresponding HBM2E DRAM read address.

AXI Address Definition

The lower 30 bits of the AXI address identify a location within the targeted pseudo-channel. The HBM2E DRAM addressing consists of the following:

  • 15-bit wide row address.
  • 6-bit wide column address. The user logic drives column address bits COL[5:1], while the controller sets the lower order column address bit COL[0] to 0. For pBL8 transactions, the user logic must set COL[1] to 0.
  • 4-bit wide bank address. Bank group corresponds to the higher order 2 bits of the bank address (BA[3:2]). HBM accesses are more efficient when the controller is able to schedule consecutive HBM2E memory device read and write commands to different bank groups.
  • 1-bit wide Stack ID (SID) is available only in the 16GB configuration.
Figure 15. AXI Address Definition

HBM2E IP AXI Channel Descriptions

Within the HBM2E IP, the AXI interface signals of the HBM2E controller follow the pattern ch<x>_u<y>_<portname> where x is the channel number and y is the pseudo-channel number. For example, ch0_u1_awid refers to the write address ID of the AXI interface corresponding to channel 0 and pseudo-channel 1. These AXI interfaces are not user-accessible.

The signals in the following tables refer to the signal names corresponding to a single AXI interface: channel 0, pseudo-channel 0.

Table 23.  Write Address (Command) Channel
Port Name Width Direction Description
ch0_u0_awaddr 30 Input Write address. The write address gives the address of the first transfer in a write burst transaction.
ch0_u0_awburst 2 Input Burst type. The burst type and length determine how the address for each transfer within the burst is calculated.
Value Burst Type
2’b01 INCR
Note: Only INCR Burst Type is supported for HBM accesses.
ch0_u0_awid 7 Input Write address channel command ID tag.
ch0_u0_awlen 8 Input Burst Length. The burst length gives the exact number of transfers in an AXI burst. In BL4 mode the HBMC supports burst lengths of 1 or 2; in BL8 mode the HBMC only supports a burst length of 2. When your design uses a burst length of greater than 2, the NOC initiator hardware issues multiple AXI commands of burst length 1 or 2 to the HBMC. Note that AXI encodes a burst length of 1 as awlen = 0, and burst length 2 is encoded as awlen = 1.
ch0_u0_awprot 3 Input Protection Type. [Reserved for future use] This signal indicates the privilege and security level of the transaction, and whether the transaction is a data access or an instruction access.
Value Protection
3’b010 No protection.
Because secure transactions are not currently supported by the HBM controller, this value must be driven to 3’b010.
ch0_u0_awqos 4 Input Quality-of-service identifier for this write command. The HBM controller supports only two priority levels, distinguished by the top bit of the QoS signal.
Value Priority
4'b1xxx High priority.
4'b0xxx Normal priority.
ch0_u0_awready 1 Output Write Address Channel Ready. This signal indicates that the slave is ready to accept an address and associated control signals.
ch0_u0_awsize 3 Input Burst Size. This signal indicates the number of AXI byte lanes containing valid data in each transfer of the burst.
Note: The HBM controller supports only 256/288-bits (32 bytes) access, burst size must be driven to 3’b101.
ch0_u0_awuser 14 Input Intel-defined signals: auto-precharge is signaled on awuser[0]. awuser[13:1] must be driven to 13'b0 at the HBM controller interface.
ch0_u0_awvalid 1 Input Write Address Channel Valid. This signal indicates that valid write address and control information are available.
ch0_u0_awlock 1 Input Lock Type [Reserved for future use].
Table 24.  Write Data Channel
Port Name Width Direction Description
ch0_u0_wdata 256 Input Write Data.
ch0_u0_wlast 1 Input Write Last. This signal indicates the last transfer in a write burst.
ch0_u0_wready 1 Output Write Channel Ready. This signal indicates that the slave (HBM controller) can accept the write data.
ch0_u0_wstrb 32 Input Write Strobes (Byte Enables). This signal indicates which byte lanes (for ch0_u0_wdata) hold valid data. There is one write strobe bit for each eight bits of the write data bus.
ch0_u0_wuser 32 Input Intel-defined signal: when the pseudo-channel's Data Mode is set to 288-bit, the ECC bits of the HBM device receive their value from wuser.
ch0_u0_wvalid 1 Input Write Channel Valid. This signal indicates that valid write data and strobes are available.
Table 25.  Write Response Channel
Port Name Width Direction Description
ch0_u0_bid 7 Output Response ID Tag. This signal is the ID tag of the write response, and matches the ID tag of the command for which this is the response.
ch0_u0_bready 1 Input Write Response Channel Ready. This signal indicates that the master can accept a write response.
ch0_u0_bresp 2 Output Write Response. This signal indicates the result of the write command.
Value Meaning
2’b00 OKAY
2’b10 SLVERR (indicates an unsuccessful transaction)
ch0_u0_bvalid 1 Output Write Response Channel Valid. This signal indicates that a valid write response is available.
Table 26.  Read Address (Command) Channel
Port Name Width Direction Description
ch0_u0_araddr 30 Input Read Address. The read address gives the address of the first transfer in a read burst transaction.
ch0_u0_arburst 2 Input Burst type. The burst type and length determine how the address for each transfer within the burst is calculated.
Value Burst Type
2’b01 INCR
Note: Only INCR Burst Type is supported by the HBM controller.
ch0_u0_arid 7 Input Read address channel command ID tag.
ch0_u0_arlen 8 Input Burst Length. The burst length gives the exact number of transfers in an AXI burst. In BL4 mode the HBMC supports burst lengths of 1 or 2; in pseudo-BL8 mode the HBMC only supports a burst length of 2. When your design uses a burst length of greater than 2, the NOC initiator hardware issues multiple AXI commands of burst length 1 or 2 to the HBMC. Note that AXI encodes a burst length of 1 as arlen = 0, and burst length 2 is encoded as arlen = 1.
ch0_u0_arprot 3 Input Protection Type. [Reserved for future use.] This signal indicates the privilege and security level of the transaction, and whether the transaction is a data access or an instruction access.
Value Protection
3’b010 No protection.

Because secure transactions are currently not supported by the HBM controller, this value must be driven to 3’b010.

ch0_u0_arqos 4 Input Quality-of-service identifier for this read command. The HBM controller supports only two priority levels, distinguished by the top bit of the QoS signal.
Value Priority
4'b1xxx High Priority.
4'b0xxx Normal Priority.
ch0_u0_arready 1 Output Read Address Ready. This signal indicates that the slave is ready to accept an address and associated control signals.
ch0_u0_arsize 3 Input Burst Size. This signal indicates the number of AXI byte lanes containing valid data in each transfer in the burst. NOTE: The HBM controller supports only 256/288-bits (32 bytes) access, burst size must be driven to 3’b101.
ch0_u0_aruser 14 Input Intel-defined signals: auto-precharge is signaled on aruser[0]. aruser[13:1] must be driven to 13'b0 at the HBM controller interface.
ch0_u0_arvalid 1 Input Read Address Valid. This signal indicates that valid read address and control information are available.
ch0_u0_arlock 1 Input Lock Type [Reserved for future use].
Table 27.  Read Data Channel
Port Name Width Direction Description
ch0_u0_rdata 256 Output Read Data.
ch0_u0_rid 7 Output Read Response ID Tag. This signal is the ID tag for the read response, and matches the ID tag of the command for which this is the response.
ch0_u0_rlast 1 Output Read Last. This signal indicates the last transfer in a read burst.
ch0_u0_rready 1 Input Read Response Channel Ready. This signal indicates that the master can accept the read data and response information.
ch0_u0_rresp 2 Output Read Response. This signal indicates the result of the read command.
Value Meaning
2’b00 OKAY
2’b10 SLVERR (indicates an unsuccessful transaction)
ch0_u0_ruser 32 Output Intel-defined signal: when the pseudo-channel's Data Mode is set to 288-bit, this signal receives its value from the ECC bits of the HBM device.
ch0_u0_rvalid 1 Output Read Valid. This signal indicates that a valid read response is available.