GTS Transceiver PHY User Guide: Agilex™ 3 FPGAs and SoCs

ID 848344
Date 8/04/2025
Public
Document Table of Contents

3.7.5.1. Reference Clock Buffer Register Information

The reference clock buffer register is located at address 0x0A6038[31:0].

Initial Reference Clock Status Bits

The read-only bits[7:0] at address 0x0A6038 contain the initial reference clock enable status. These bits indicate the initial buffer settings in the bitstream. The bits are updated only once after the bitstream loads. The bit values indicate the following:
  • 1: Indicates that the buffer is used and activated.
  • 0: Indicates that the buffer is unused and deactivated.
The definition of the bit fields is as follows:
  • Bit[0]: Local reference clock buffer bank 0
  • Bit[1]: Regional reference clock buffer bank 0
  • Bit[7:2]: Reserved
For example, a value of in bits[7:0] indicates that the bitstream has enabled the reference clock buffer as follows:
  • Local reference clock in bank 0

Live Reference Clock Buffer Status Bits

The read-only bits[15:8] at address 0x0A6038 provide the live reference clock buffer status. These bits indicate the current status of the buffer, and whether it has been turned off. The bit values indicate the following:
  • 1: Indicates that the buffer has been turned off by the protection circuitry.
  • 0: Indicates that the buffer is still on. This setting is only valid if the respective reference clock buffers are initially enabled in the design, as indicated in status bits [7:0].
The definition of the bit fields is as follows:
  • Bit[8]: Local reference clock buffer bank 0
  • Bit[9]: Regional reference clock buffer bank 0
  • Bit[15:10]: Reserved
For example, a value of 8’b00000010 in bits[15:8] indicates the status of reference clock buffers as follows:
  • Regional reference clock from bank 0 is turned off

Re-enabling Reference Clock Buffer Request Bits

The read-write bits[23:16] are used to request re-enabling the reference clock buffers. You can set these bits once the input reference clock is running and stable again. These are self clearing bits which are cleared once the request is accepted. The bit values indicate the following:
  • 1: Used to send a request to re-enable the clock buffer.
  • 0: Self-cleared once the request is accepted.
The definition of the bit fields is as follows:
  • Bit[16]: Re-enable Local reference clock buffer bank 0
  • Bit[17]: Re-enable Regional reference clock buffer bank 0
  • Bit[23:18]: Reserved
For example, writing 8’b00000010 to bits[23:16] sends a request to re-enable the regional reference clock buffer in bank 0.

The bits[15:0] at address 0x0A6038 are read-only, and must never be written to. Overwriting these bits may cause unexpected behavior. You must only perform write operations to bits[23:16]. In addition, you must only use byte access to write to this register, to avoid overwriting the read-only bits and must not use a 32 bit read-modify-write access for this register.