GTS Transceiver PHY User Guide

ID 817660
Date 4/01/2024
Public

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3.10.3. Logical Avalon® Memory-Mapped Port Indexing

This section explains how to access the GTS PMA lanes if your design has more than one GTS PMA lane. You need to know how to control the logical Avalon® memory-mapped port indexing if you are using the shared reconfiguration interface. (Enable separate Avalon interface per PMA = Off).

If your design has the Enable separate Avalon interface per PMA = On feature enabled, each Avalon® memory-mapped interface has its own reconfiguration interface and you can directly access the port’s register address without following the logical port indexing instruction explained in this section.

The reconfiguration address bus for one PMA lane in the IP is:
  • 18 bits for the PMA Avalon memory-mapped reconfiguration interface (i_reconfig_address[17:0])

The reconfiguration address space grows as a function of the following equation:

log2(N)

(where N = number of lanes), for an increase in the number of PMA lanes. The additional MSB bits of the reconfiguration address bus represent the logical Avalon® memory-mapped port index value. Refer to MSB Address Bits for PMA Logical Avalon® Memory-Mapped Reconfiguration Port Index Value for more information.

For example, if you enable four PMA lanes in your design, for the Avalon® memory-mapped interface, the total reconfiguration address bus is i_reconfig_address[19:0]. The Avalon® memory-mapped interfaces MSB address bits (i_reconfig_address[19:18]) provide the logical mapping to access different lanes based on the number of PMA lanes. The two additional MSB address bits (i_reconfig_address[19:18]) are a logical representation of the Avalon® memory-mapped interface port. You can use them to read or write to the individual Avalon® memory-mapped interface defined within the IP.

The following table shows the MSB address bits for logical Avalon® memory-mapped port indexing with the number of PMA lanes configured in the IP.

Table 49.  MSB Address Bits for Logical Avalon® Memory-Mapped Reconfiguration Port Index Value
PMA Lane Set in GUI Reconfiguration Address Bus 32 MSB Address Bits for Logical Avalon® Memory-Mapped Port Indexing Logical Avalon® Memory-Mapped Port Indexing (value=hex)
1 i_reconfig_address[17:0] Not Applicable 0
2 i_reconfig_address[18:0] [18] 0,1
4 i_reconfig_address[19:0] [19:18] 0,1,2,3
6, 8 i_reconfig_address[20:0] [20:18] 0,1,2,3,4,5,6,7

Example 1: Performing a Read Operation for TX EQ pre_tap_1 Register (0x097830) in Simulation

For example, if your design has two PMA lanes enabled in the IP GUI, the reconfiguration address bus width is i_reconfig_address[18:0], which has one additional MSB address bit. This is to provide address space when you are performing read operation for lane 0 and lane 1. You need to convert the byte address (from the register map file) to word address format (byte/4) in order to use it in your testbench, as shown in the following example.
  • For lane 0: 0x97830 ÷ 4 = 0x25E0C
  • For lane 1: 0x197830 ÷ 4 = 0x65E0C
Note: Alternatively, you can add 0x40000h to the word address for each incremental lane up to lane 7 (0x1E5E0C), depending on how many PMA lanes you enable in the IP GUI.
Figure 57. Example of Verilog Testbench Code When Performing Read Operation to TX EQ Address
avmm_read(21'h25E0C,rdata,32'habcd_ef01,1); // To read TX EQ for lane 0
repeat (5) @(posedge mgmt_clk);
avmm_read(21'h65E0C,rdata,32'habcd_ef01,1); // To read TX EQ for lane 1
repeat (5) @(posedge mgmt_clk);
32 The address bus is referring to word addressing format used when you use register transfer level language in your design for read and write operation to the Avalon® memory-mapped interface defined within the IP.