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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 |
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| 26 | 25 | 16 |
| Reserved |
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| RNDNUM |
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15 | 12 | 11 | 10 | 9 | 0 |
| COLLCOUNT | Reserved |
| TXBACKOFF | |
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LEGEND: R = Read only;
Table 63. Back Off Test Register (BOFFTEST) Field Descriptions
Bit | Field | Value | Description |
Reserved | 0 | Reserved | |
RNDNUM |
| Backoff random number generator. This field allows the Backoff Random Number Generator to be | |
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| read. Reading this field returns the generator'scurrent value. The value is reset to 0 and begins |
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| counting on the clock after the deassertion of reset. |
COLLCOUNT | Collision count. These bits indicate the number of collisions the current frame has experienced. | ||
Reserved | 0 | Reserved | |
TXBACKOFF | Backoff count. This field allows the current value of the backoff counter to be observed for test | ||
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| purposes. This field is loaded automatically according to the backoff algorithm, and is decremented |
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| 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 |
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| 16 |
| Reserved |
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15 | 5 | 4 | 0 |
Reserved |
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| PACEVAL |
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LEGEND: R = Read only;
Table 64. Transmit Pacing Algorithm Test Register (TPACETEST) Field Descriptions
Bit | Field | Value | Description |
Reserved | 0 | Reserved | |
PACEVAL | Pacing register current value. A nonzero value in this field indicates that transmit pacing is active. A | ||
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| transmit frame collision or deferral causes PACEVAL to be loaded with 1Fh (31); good frame |
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| transmissions (with no collisions or deferrals) cause PACEVAL to be decremented down to 0. When |
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| PACEVAL is nonzero, the transmitter delays four Inter Packet Gaps between new frame transmissions |
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| after each successfully transmitted frame that had no deferrals or collisions. If a transmit frame is |
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| deferred or suffers a collision, the IPG time is not stretched to four times the normal value. Transmit |
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| pacing helps reduce capture effects, which improves overall network bandwidth. |
102 Ethernet Media Access Controller (EMAC)/SPRU941A
Management Data Input/Output (MDIO) | Submit Documentation Feedback |
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