I347-AT4 Datasheet, PDF (49/148 Pages) Intel Corporation – Intel® Ethernet Network Connection I347-AT4 Datasheet

Device Functionality—I347-AT4
Table 16.
Once an error event is captured, register 20_2.15 is set to 1b indicating that the
capture data is valid. No further errors are captured until all captured registers are
read. Register 20_2.13:12 is set to 00b. Register 20_2.9:0 outputs the byte that is the
earliest received. Once register 20_2 is read register 20_2.13:12 increments and
register 20_2.9.0 is updated with the next earliest byte. The register is incremented
and byte updated until the fourth read occurs. After the fourth read to register 20_2
completes, register 20_2.15 is set to 0b and the error capturing resumes four RX_CLK
cycles after the final read completes. The 4 RX_CLK cycle delay is required to insure
that the register has four valid bytes loaded prior to being frozen. Note that a side
effect of doing this is the RX_ER might be high in the captured bytes.
Error Byte Capture
3.15
Register
20_2.15
Function
Capture Data Valid
20_2.13:12
Byte Number
20_2.9
RX_ER
20_2.8
20_2.7:0
RX_DV
RXD[7:0]
Setting
1b = Bits 14:0 valid.
0b = Bits 14:0 invalid.
00b = 4 bytes before RX_ER asserted.
01b = 3 bytes before RX_ER asserted.
10b = 2 bytes before RX_ER asserted.
11b = 1 byte before RX_ER asserted.
The byte number increments after every read when register
20_2.15 is set to 1b.
RX Error.
Normally this bit is low since the capture is triggered by RX_ER
being high.
However, it is possible to see an RX_ER high when the capture is
re-enabled after reading the fourth byte and there happens to be a
long sequence of RX_ER when the capture restarts.
RX Data Valid.
RX Data.
MDI/MDIX Crossover
The I347-AT4 automatically determines whether or not it needs to cross over between
pairs as listed in Table 17 so that an external crossover cable is not required. If the
I347-AT4 interoperates with a device that cannot automatically correct for crossover,
the I347-AT4 makes the necessary adjustment prior to commencing auto-negotiation.
If the I347-AT4 interoperates with a device that implements MDI/MDIX crossover, a
random algorithm as described in IEEE 802.3 clause 40.4.4 determines which device
performs the crossover.
When the I347-AT4 interoperates with legacy 10BASE-T devices that do not implement
auto-negotiation, the I347-AT4 follows the same algorithm as previously described
since link pulses are present. However, when interoperating with legacy 100BASE-TX
devices that do not implement auto-negotiation (such as, link pulses are not present),
the I347-AT4 uses signal detect to determine whether or not to crossover.
The auto MDI/MDIX crossover function can be disabled via register 16_0.6:5.
The pin mapping in MDI and MDIX modes is listed in Table 17.
39