Freescale Semiconductor MPC860T user manual Initialization Sequence, Hardware Initialization

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		Freescale Semiconductor, Inc.
		Table 6-24. X_CNTRL Field Descriptions
Bits	Name	Description
31	GTS	Graceful transmit stop. When GTS is set, the MAC stops transmission after any frame being
		transmitted is complete and INTR_EVENT[GRA] is set. If frame transmission is not underway, the
		GRA interrupt is asserted immediately. When transmission completes, clearing GTS causes the
		next frame in the transmit FIFO to be sent. If an early collision occurs during transmission when
		GTS = 1, transmission stops after the collision. The frame is sent again once GTS is cleared. Note
		that there may be old frames in the transmit FIFO that are sent when GTS is reasserted. To avoid
		this, clear ECNTRL[ETHER_EN] after the GRA interrupt.

6.3 Initialization Sequence

This section describes which registers and RAM locations are reset due to hardware reset, which are reset due to the microcontroller, and what locations the user must initialize before enabling the FEC.

6.3.1 Hardware Initialization

In the FEC, only registers that generate interrupts to the PowerPC processor or cause conßict on bidirectional buses are reset by hardware. The registers shown in Table 6-25 are reset due to a hardware reset.

Table 6-25. Hardware Initialization

User/System	Register/Machine	Reset Value
User	ECNTRL	Cleared
User	IEVENT	Cleared
User	IMASK	Cleared
User	MII.SPEED	Cleared
User	PORT DPAR	Cleared
User	PORT DIR	Cleared

Other registers are reset whenever ECNTRL[ETHER_EN] is cleared. Clearing ETHER_EN immediately stops all DMA accesses and stops transmit activity after a bad CRC is sent; refer to Table 6-26.

Table 6-26. ECNTRL[ETHER_EN] Deassertion Initialization

User/System	Register/Machine	Reset Value
User	R_DES_ACTIVE	Cleared
User	X_DES_ACTIVE	Cleared

6.3.2 User Initialization (before Setting ECNTRL[ETHER_EN])

The user must initialize portions of the FEC before setting ECNTRL[ETHER_EN]. The

6-22MPC860T (Rev. D) Fast Ethernet Controller Supplement MOTOROLA

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