External Memory Interface Handbook Volume 3: Reference Material: For UniPHY-based Device Families
1.13.2. AFI Parameters
The parameters described in the following tables affect the width of AFI signal buses. Parameters prefixed by MEM_IF_ refer to the signal size at the interface between the PHY and memory device.
| Parameter Name |
Description |
|---|---|
| AFI_RATE_RATIO |
The ratio between the AFI clock frequency and the memory clock frequency. For full-rate interfaces this value is 1, for half-rate interfaces the value is 2, and for quarter-rate interfaces the value is 4. |
| DATA_RATE_RATIO |
The number of data bits transmitted per clock cycle. For single-date rate protocols this value is 1, and for double-data rate protocols this value is 2. |
| ADDR_RATE_RATIO |
The number of address bits transmitted per clock cycle. For single-date rate address protocols this value is 1, and for double-data rate address protocols this value is 2. |
| Parameter Name |
Description |
|---|---|
| MEM_IF_ADDR_WIDTH |
The width of the address bus on the memory device(s). |
| MEM_IF_BANKADDR_WIDTH |
The width of the bank address bus on the interface to the memory device(s). Typically, the log 2 of the number of banks. |
| MEM_IF_CS_WIDTH |
The number of chip selects on the interface to the memory device(s). |
| MEM_IF_WRITE_DQS_WIDTH |
The number of DQS (or write clock) signals on the write interface. For example, the number of DQS groups. |
| MEM_IF_CLK_PAIR_COUNT |
The number of CK/CK# pairs. |
| MEM_IF_DQ_WIDTH |
The number of DQ signals on the interface to the memory device(s). For single-ended interfaces such as QDR II, this value is the number of D or Q signals. |
| MEM_IF_DM_WIDTH |
The number of data mask pins on the interface to the memory device(s). |
| MEM_IF_READ_DQS_WIDTH |
The number of DQS signals on the read interface. For example, the number of DQS groups. |
| Parameter Name |
Derivation Equation |
|---|---|
| AFI_ADDR_WIDTH |
MEM_IF_ADDR_WIDTH * AFI_RATE_RATIO * ADDR_RATE_RATIO |
| AFI_BANKADDR_WIDTH |
MEM_IF_BANKADDR_WIDTH * AFI_RATE_RATIO * ADDR_RATE_RATIO |
| AFI_CONTROL_WIDTH |
AFI_RATE_RATIO * ADDR_RATE_RATIO |
| AFI_CS_WIDTH |
MEM_IF_CS_WIDTH * AFI_RATE_RATIO |
| AFI_DM_WIDTH |
MEM_IF_DM_WIDTH * AFI_RATE_RATIO * DATA_RATE_RATIO |
| AFI_DQ_WIDTH |
MEM_IF_DQ_WIDTH * AFI_RATE_RATIO * DATA_RATE_RATIO |
| AFI_WRITE_DQS_WIDTH |
MEM_IF_WRITE_DQS_WIDTH * AFI_RATE_RATIO |
| AFI_LAT_WIDTH |
6 |
| AFI_RLAT_WIDTH |
AFI_LAT_WIDTH |
| AFI_WLAT_WIDTH |
AFI_LAT_WIDTH * MEM_IF_WRITE_DQS_WIDTH |
| AFI_CLK_PAIR_COUNT |
MEM_IF_CLK_PAIR_COUNT |
| AFI_WRANK_WIDTH |
Number of ranks * MEM_IF_WRITE_DQS_WIDTH *AFI_RATE_RATIO |
| AFI_RRANK_WIDTH |
Number of ranks * MEM_IF_READ_DQS_WIDTH *AFI_RATE_RATIO |