3.1.5. SYSREF Generator
The SYSREF generator in the design example is used for the duplex JESD204C IP link initialization demonstration purpose only. In the JESD204C subclass 1 system level application,you must generate SYSREF from the same source as the device clock.
For the F-Tile JESD204C IP, the SYSREF multiplier (SYSREF_MULP) of the SYSREF control register defines the SYSREF period, which is n-integer multiple of the E parameter.
You must ensure E*SYSREF_MULP ≤16. For example, if E=1, the legal setting for SYSREF_MULP must be within 1–16, and if E=3, the legal setting for SYSREF_MULP must be within 1–5.
You can select whether you want the SYSREF type to be a one-shot pulse, periodic, or gapped periodic through the Example Design tab in the F-Tile JESD204C Intel® FPGA IP parameter editor.
E | SYSREF_MULP | SYSREF PERIOD (E*SYSREF_MULP*32) |
Duty Cycle | Description |
---|---|---|---|---|
1 | 1 | 32 | 1..31 (Programmable) |
Gapped Periodic |
1 | 1 | 32 | 16 (Fixed) |
Periodic |
1 | 2 | 64 | 1..63 (Programmable) |
Gapped Periodic |
1 | 2 | 64 | 32 (Fixed) |
Periodic |
1 | 16 | 512 | 1..511 (Programmable) |
Gapped Periodic |
1 | 16 | 512 | 256 (Fixed) |
Periodic |
2 | 3 | 192 | 1..191 (Programmable) |
Gapped Periodic |
2 | 3 | 192 | 96 (Fixed) |
Periodic |
2 | 8 | 512 | 1..511 (Programmable) |
Gapped Periodic |
2 | 8 | 512 | 256 (Fixed) |
Periodic |
2 | 9 (Illegal) |
64 | 32 (Fixed) |
Gapped Periodic |
2 | 9 (Illegal) |
64 | 32 (Fixed) |
Periodic |
Bits | Default Value | Description |
---|---|---|
sysref_ctrl[1:0] |
|
SYSREF type. The default value depends on the SYSREF mode setting in the Example Design tab in the F-Tile JESD204C Intel® FPGA IP parameter editor. |
sysref_ctrl[6:2] | 5'b00001 | SYSREF multiplier. This SYSREF_MULP field is applicable to periodic and gapped-periodic SYSREF type. You must configure the multiplier value to ensure the E*SYSREF_MULP value is between 1 to 16 before the F-Tile JESD204C IP is out of reset. If the E*SYSREF_MULP value is out of this range, the multiplier value defaults to 5'b00001. |
sysref_ctrl[7] |
|
SYSREF select. The default value depends on the data path setting in the Example Design tab in the F-Tile JESD204C Intel® FPGA IP parameter editor.
|
sysref_ctrl[16:8] | 9'h0 | SYSREF duty cycle when SYSREF type is periodic or gapped periodic. You must configure the duty cycle before the F-Tile JESD204C IP is out of reset. Maximum value = (E*SYSREF_MULP*32)-1 For example: 50% duty cycle = (E*SYSREF_MULP*32)/2 The duty cycle defaults to 50% if you do not configure this register field, or if you configure the register field to 0 or more than the maximum value allowed. |
sysref_ctrl[17] | 1'b0 | Manual control when SYSREF type is one-shot.
You need to write a 1 then a 0 to create a SYSREF pulse in one-shot mode. |
sysref_ctrl[31:18] | 22'h0 | Reserved. |