SBAA543 July   2022 AFE7900 , AFE7920 , AFE7950

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2JESD204C
    1. 2.1 Basic Review of JESD204C Protocol
    2. 2.2 Finding Optimal RBD for JESD204C
  5. 3JESD204B
    1. 3.1 Basic Review of JESD204B Protocol
    2. 3.2 Finding Optimal RBD for JESD204B
  6. 4Setting RBD in AFE79xx
    1. 4.1 Register Map
    2. 4.2 Setting RBD in Configuration Sequence
    3. 4.3 Finding Optimal RBD using CAPI
      1. 4.3.1 Use Case with 1 JESD Links
      2. 4.3.2 Use Case with 2 JESD Links
      3. 4.3.3 Use Case with 3 JESD Links
      4. 4.3.4 Use Case with 4 JESD Links
  7. 5Fixing Potential Alarms Related to RBD
    1. 5.1 RBD Alarm
    2. 5.2 SoEMB Close to LEMC Edge
    3. 5.3 Start of ILA Close to LMFC Edge
  8. 6References

5.3 Start of ILA Close to LMFC Edge

It is possible that when the start of ILA is close to LMFC edge, some of lane0/1/2/3_f_counter_any_lane_ready read a very small value close to 0, and some lanes read values close to maximum value of fcounter (31 when K=32 and F=4). The buffer index is essentially a circular indexing as the buffer has to absorb both advancements and delays in time. Such a case is shown in Figure 5-2(1).

Initially, the lane0/1/2/3_f_counter_any_lane_ready registers read from the range of (30,31,0,1,2). Specifically, lane0_f_counter_any_lane_ready reads 30 and lane3_f_counter_any_lane_ready reads 2. In such cases, it is recommended to shift the LMFC counter by writing to link0_init_f_counter, so that all fcounter values are close by values.

On rising edge of LMFC, the counter starts from value of link0_init_o_counter/4. In other words, the LMFC counter is shifted by link0_init_o_counter/4 × F. In JESD204B, the link0_init_o_counter can only be programmed to values that are multiples of 4.

In Figure 5-2, link0_init_o_counter is set to 28 (In this case F is assumed to be 1). With this, lane0_f_counter_any_lane_ready reads ((30+28/4)%32) = 5 and lane3_f_counter_any_lane_ready reads 2+28/4 = 9. RBD is set as 13 which has a margin of 4 from the last arriving lane.

Note that the RBD value is also with reference to the shifted LMFC counter.

This can be done in Latte by setting the following paramter:

sysParams.jesdRxInitLmfcCounter = 7

Figure 5-2 JESD204B LMFC Edge Close to Start of ILA
1.

Parts of figures were based on JEDEC JESD204C standard, Figure 5 and Figure 50. Copyright JEDEC. Modifications have not been approved by and do not reflect the views of JEDEC.