Texas Instruments TMS320DM643X DMP manual Back Off Test Register Bofftest

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Ethernet Media Access Controller (EMAC) Registers

5.38 Back Off Test Register (BOFFTEST)

The back off test register (BOFFTEST) is shown in Figure 64 and described in Table 63.

Figure 64. Back Off Random Number Generator Test Register (BOFFTEST)

31			26	25	16
	Reserved				RNDNUM
	R-0				R-0
15	12	11	10	9	0
	COLLCOUNT	Reserved			TXBACKOFF
	R-0		R-0		R-0

LEGEND: R = Read only; -n= value after reset

Table 63. Back Off Test Register (BOFFTEST) Field Descriptions

Bit	Field	Value	Description
31-26	Reserved	0	Reserved
25-16	RNDNUM	0-3FFh	Backoff random number generator. This field allows the Backoff Random Number Generator to be
			read. Reading this field returns the generator'scurrent value. The value is reset to 0 and begins
			counting on the clock after the deassertion of reset.
15-12	COLLCOUNT	0-Fh	Collision count. These bits indicate the number of collisions the current frame has experienced.
11-10	Reserved	0	Reserved
9-0	TXBACKOFF	0-3FFh	Backoff count. This field allows the current value of the backoff counter to be observed for test
			purposes. This field is loaded automatically according to the backoff algorithm, and is decremented
			by one for each slot time after the collision.

5.39 Transmit Pacing Algorithm Test Register (TPACETEST)

The transmit pacing algorithm test register (TPACETEST) is shown in Figure 65 and described in Table 64.

Figure 65. Transmit Pacing Algorithm Test Register (TPACETEST)

31			16
	Reserved
	R-0
15	5	4	0
Reserved			PACEVAL
R-0			R-0

LEGEND: R = Read only; -n= value after reset

Table 64. Transmit Pacing Algorithm Test Register (TPACETEST) Field Descriptions

Bit	Field	Value	Description
31-5	Reserved	0	Reserved
4-0	PACEVAL	0-1Fh	Pacing register current value. A nonzero value in this field indicates that transmit pacing is active. A
			transmit frame collision or deferral causes PACEVAL to be loaded with 1Fh (31); good frame
			transmissions (with no collisions or deferrals) cause PACEVAL to be decremented down to 0. When
			PACEVAL is nonzero, the transmitter delays four Inter Packet Gaps between new frame transmissions
			after each successfully transmitted frame that had no deferrals or collisions. If a transmit frame is
			deferred or suffers a collision, the IPG time is not stretched to four times the normal value. Transmit
			pacing helps reduce capture effects, which improves overall network bandwidth.

102 Ethernet Media Access Controller (EMAC)/SPRU941A –April 2007

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