K60P100M100SF2RM Datasheet, PDF (1208/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
The correction counter operates fully independently and increments by one with each
time-stamping clock cycle. When it reaches the value configured in ENETn_ATCOR, it
restarts and instructs the timer once to increment by the correction value, instead of the
normal value. The normal and correction increments are configured in ENETn_ATINC.
To speed up the timer, set the correction increment more than the normal increment
value. To slow down the timer, set the correction increment less than the normal
increment value. The correction counter only defines the distance of the corrective
actions, not the amount. This allows very fine corrections and low jitter (in the range of 1
ns) independent of the chosen clock frequency.
By enabling slave mode (ENETn_ATCR[SLAVE] = 1) the timer is ignored and the
current time is externally provided from one of the external modules. See the Chip
Configuration details for which clock source is used. This is useful if multiple modules
within the system must operate from a single timer. When slave mode is enabled, you
still must set ENETn_ATINC[INC] to the value of the master, since it is used for internal
comparisons.
44.4.10.2 Transmit Timestamping
Only 1588 event frames need to be time-stamped on transmit. The client application (e.g.
the MAC driver) should detect 1588 event frames and set TxBD[TS] together with the
frame.
If TxBD[TS] is set, the MAC records the timestamp for the frame in ENETn_ATSTMP.
ENETn_EIR[TS_AVAIL] is set to indicate that a new timestamp is available.
Software implements a handshaking procedure by setting TxBD[TS] when it transmits
the frame it needs a timestamp for and then waits for ENETn_EIR[TS_AVAIL] to know
when the timestamp is available. It then can read the timestamp from ENETn_ATSTMP.
This is done for all event frames. Other frames do not use TxBD[TS] and, therefore, do
not interfere with the timestamp capture.
44.4.10.3 Receive Timestamping
When a frame is received, the MAC latches the value of the timer when the frame's SFD
(start of frame delimiter) field is detected and provides the captured timestamp on
RxBD[1588 timestamp]. This is done for all received frames.
1208
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.