High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9312
157
Revision 1.4 (08-19-08)
DATASHEET
Clock synchronization and hardware processing between the network data and the time stamp capture
hardware causes the time stamp point to be slightly delayed. The host software can account for this
delay, as it is fairly deterministic.
details the time stamp capture delay as a function of the
mode of operation. Refer to
Chapter 7, "Ethernet PHYs," on page 82
for details on these modes.
Once the packet type is matched, according to
, and the Frame Check Sequence (FCS) is
verified, the following occurs:
The time stamp is loaded into the corresponding ports’ capture registers:
–On Reception:
Port x 1588 Clock High-DWORD Receive Capture Register
and
Port x 1588 Clock Low-DWORD Receive Capture
Register (1588_CLOCK_LO_RX_CAPTURE_x)
–On Transmission:
Port x 1588 Clock High-DWORD Transmit Capture Register
Port x 1588 Clock Low-DWORD Transmit Capture
Register (1588_CLOCK_LO_TX_CAPTURE_x)
The Sequence ID and Source UUID are loaded into the corresponding ports’ registers:
–On Reception:
Port x 1588 Sequence ID, Source UUID High-WORD Receive Capture Register
(1588_SEQ_ID_SRC_UUID_HI_RX_CAPTURE_x)
and
DWORD Receive Capture Register (1588_SRC_UUID_LO_RX_CAPTURE_x)
–On Transmission:
Port x 1588 Sequence ID, Source UUID High-WORD Transmit Capture
Register (1588_SEQ_ID_SRC_UUID_HI_TX_CAPTURE_x)
Low-DWORD Transmit Capture Register (1588_SRC_UUID_LO_TX_CAPTURE_x)
The corresponding maskable interrupt flag is set in the
1588 Interrupt Status and Enable Register
Section 11.6, "IEEE 1588 Interrupts," on page 160
for information
on IEEE 1588 interrupts.)
Note:
Packets that do not contain an integral number of octets are not considered valid and do not
cause a capture.
11.2.1
Capture Locking
The corresponding ports’ clock capture, sequence ID, and source UUID registers can be optionally
locked when a capture event occurs, preventing them from being overwritten until the host clears the
corresponding interrupt flag in the
1588 Interrupt Status and Enable Register (1588_INT_STS_EN)
.
This is accomplished by setting the corresponding lock enable bit(s) in the
. Each port has two lock enable control bits within this register, which allow the receive
and transmit portions of each port to be locked independently. In addition, a lock enable bit is provided
for each time stamp enabled GPIO (LOCK_ENABLE_GPIO_8 and LOCK_ENABLE_GPIO_9) which
prevents the corresponding GPIO clock capture registers from being overwritten when the GPIO
interrupt in
1588 Interrupt Status and Enable Register (1588_INT_STS_EN)
is set. Refer to
14.2.5.22, "1588 Configuration Register (1588_CONFIG)," on page 222
for additional information on
the capture locking related bits.
Table 11.2 Time Stamp Capture Delay
MODE OF OPERATION
DELAY (+/- 10 nS)
100 Mbps
30 nS
10 Mbps
120 nS