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Ethernet MAC
External PHY
MOSC
PTPCEN
RX+
RX-
TX+
TX-
EN0RXER
EN0RXCK
EN0RXD3
EN0RXDV
EN0TXCK
EN0TXD3
EN0TXER
EN0TXEN
EN0COL
EN0CRS
EN0MDIO
EN0MDC
EN0INTRN
EN0RXD2
EN0RXD1
EN0RXD0
EN0TXD2
EN0TXD1
EN0TXD0
Gated SYSCLK
PTP_REFCLK
MAC Control
and Status
Registers
EMACCC
MSP432E4
Microcontroller
Typically
25-MHz
Crystal
Functional Description
886
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
Figure 15-3. MII Clock Structure
15.3.1.3 Reduced Media-Independent Interface (RMII)
Three clock sources interface to the Ethernet MAC in an RMII configuration, as follows:
•
Gated system clock (SYSCLK): The SYSCLK signal acts as the clock source to the Control and Status
registers (CSR) of the Ethernet MAC. The SYSCLK frequency for Run, Sleep, and Deep Sleep mode
is programmed in the System Control module. See
for more information on programming
SYSCLK and enabling the Ethernet MAC.
•
MOSC: A gated version of the MOSC clock is provided as the Precision Time Protocol (PTP) reference
clock (PTPREF_CLK). The MOSC clock source can be a single-ended source on the OSC0 pin or a
crystal on the OSC0 and OSC1 pins. When advanced timestamping is used and the PTP module has
been enabled by setting the PTPCEN bit in the EMACCC register, the MOSC drives PTPREF_CLK.
PTPREF_CLK has a minimum frequency requirement of 5 MHz and a maximum frequency of 25 MHz.
See
for more information.
•
EN0RREF_CLK: When using RMII, a 50-MHz external reference clock must drive the EN0RREF_CLK
input signal and the external PHY. Depending on the configuration of the FES bit in the Ethernet MAC
Configuration (EMACCFG) register, the reference clock input (EN0RREF_CLK) is divided by 20 for 10
Mbps, or 2 for 100 Mbps operation, and used as the clock for receive and transmit data.
shows the clock inputs to the RMII clock.