The architecture of the PTP timer is shown in the following figure.
Figure 1. System Timer and Adjustment Inputs Diagram (MRMAC Internal)
Note: The ctl_ptp_st_sync represents ctl_rx_ptp_st_sync and
ctl_tx_ptp_st_sync.
The heart of the timer is an accumulator with a programmable
periodic increment. You can specify the initial timer value and the increment value. These
values can be further adjusted, if necessary, using various optional correction methods
(including phase and frequency adjustments) to achieve improved accuracy between the system
timer and the master TOD timer.The main elements of the system timer include:
- system_timer
- MRMAC timer, source of generated timestamps.
- Timer Increment
- The amount by which
system_timeris incremented each clock period. The amount of increment can be set or adjusted as needed to synchronize thesystem_timerwith the external master clock. The established increment can also be temporarily bypassed to provide a specific timer adjustment.
- Overwrite
- A one-shot overwrite of the
system_timervalue, triggered by a transition ofctl_ptp_st_syncwhilectl_tx/rx_ptp_st_overwriteinput signal is set.
- Timestamp
- The generated timestamp to the system, micro-adjusted to account for any desired
latency by the value
ctl_ptp_latency_adj.