STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

Ethernet (ETH): media access control (MAC) with DMA controller
RM0008
6. Turn-off the application and transmit clock inputs to the core (and other relevant clocks
in the system) to reduce power and enter Sleep mode.
7. On receiving a valid wakeup frame, the Ethernet peripheral exits Power-down mode.
8. On receiving the interrupt, the system must enable the application and transmit clock
inputs to the Ethernet.
9. Read the ETH_MACPMTCSR register to clear the interrupt, then enable the MAC and
resume normal operation.
27.5.9 Precision time protocol (IEEE1588 PTP)
The IEEE 1588 standard defines a protocol that allows precise clock synchronization in
measurement and control systems implemented with technologies such as network
communication, local computing and distributed objects. The protocol applies to systems
that communicate by local area networks supporting multicast messaging, including (but not
limited to) Ethernet. This protocol is used to synchronize heterogeneous systems that
include clocks of varying inherent precision, resolution and stability. The protocol supports
system-wide synchronization accuracy in the submicrosecond range with minimum network
and local clock computing resources. The message-based protocol, known as the precision
time protocol (PTP), is transported over UDP/IP. The system or network is classified into
Master and Slave nodes for distributing the timing/clock information. The protocol’s
technique for synchronizing a slave node to a master node by exchanging PTP messages is
described in Figure 306.
Figure 306. Networked time synchronization
Master clock time
Slave clock time
t 1
Sync message
Data at
slave clock
t 2m
Follow_up message
containing value of t1
t 2
t 2
t 1 , t 2 , t 3
ai15669
t 1 , t 2
t 3m
t 4
t 1 , t 2 , t 3 , t 4
Delay_Req message
t 3
Delay_Resp message
containing value of t4
time
1. The master broadcasts PTP Sync messages to all its nodes. The Sync message
contains the master’s reference time information. The time at which this message
leaves the master’s system is t 1 . For Ethernet ports, this time has to be captured at the
MII.
2. A slave receives the Sync message and also captures the exact time, t 2 , using its
timing reference.
872/995 Doc ID 13902 Rev 9