TM4C129DNCZAD Datasheet, PDF (1535/1967 Pages) Texas Instruments – Tiva Microcontroller

Tiva^™ TM4C129DNCZAD Microcontroller
■ 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. Refer to “System Control” on page 226
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 Precision Timer Protocol (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. Refer to “IEEE 1588 and Advanced
Timestamp Function” on page 1567 for more information.
■ EN0RXCK: This clock signal is driven by the external PHY oscillator and is either 2.5 or 25 MHz
depending on whether the device is operating at 10 Mbps or 100 Mbps.
■ EN0TXCK This clock signal is driven by the external PHY oscillator and is either 2.5 or 25 MHz
depending on whether the device is operating at 10 Mbps or 100 Mbps.
Figure 23-2 on page 1535 depicts the clock inputs for an MII interface.
Figure 23-2. MII Clock Structure
Tiva Cortex-M4
Microcontroller
Gated SYSCLK
PTPCEN
Ethernet MAC
MAC Control /
Status Registers
EMACCC
PTP_REFCLK
EN0TXCK
EN0TXEN
EN0TXD0
EN0TXD1
EN0TXD2
EN0TXD3
EN0TXER
EN0RXCK
EN0RXDV
EN0RXD0
EN0RXD1
EN0RXD2
EN0RXD3
EN0RXER
EN0INTRN
EN0MDC
EN0MDIO
EN0CRS
EN0COL
External PHY
TX+
TX-
RX+
RX-
Typically
25MHz
Crystal
MOSC
23.3.1.2 RMII Interface
There are three clock sources that interface to the Ethernet MAC in an RMII configuration:
■ 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
June 18, 2014
Texas Instruments-Production Data
1535