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CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
61
3.16 Notes on Using
µµµµ
PD98431
(1) Connection with PHY device
If the
µ
PD98431 is connected to the PHY device of some manufacturers, a write access is not correctly
completed when MII management access is made, and the data is not correctly written to the PHY register. This
phenomenon has reportedly occurred with the following product:
•
Broadcom BCM5208
The
µ
PD98431 outputs MDC for the duration of 64 clocks to an MII management frame, from preamble to data.
Reportedly, the PHY device in which the above phenomenon occurs does not complete a write access unless
MDC is input in the "IDLE" status following the data, i.e., unless MDC is input at least for the duration of 65
clocks after preamble has been started. To avoid this phenomenon, consult each PHY device manufacturer.
(2) Automatic transmission of pause frame
If a condition in which a pause frame is automatically transmitted occurred two times or more in a short period of
time, the condition that is satisfied last is assumed to be valid and the pause frame is transmitted. Depending on
the case, however, the pause frame is transmitted two times in the condition that is satisfied last.
The pause frames automatically transmitted include the pause frame having the value of PTIME of the MACC3
register (PTIME pause frame) and pause frame with a pause timer value of 0 (0-pause frame). The PTIME
pause frame and 0-pause frame are automatically transmitted under the following conditions:
The PTIME pause frame is transmitted if the quantity of the data in the receive FIFO exceeds the value of
RFDMH of the RFIC1 register. If this condition occurs successively at short intervals, the PTIME pause frame is
transmitted once by regarding only the last condition as valid. Depending on the interval at which the condition
occurs, however, the PTIME pause frame is transmitted two times.
The 0 pause frame is transmitted if the quantity of the data in the receive FIFO falls below the value of RFDML of
the RFIC1a register after the condition for transmitting the PTIME pause frame has been satisfied. At this time,
the 0-pause frame is transmitted after the PTIME pause frame has been transmitted. If the interval at which the
quantity of the data in the receive FIFO falls below the value of RFDML of the RFIC1 register is short after the
PTIME pause frame transmission condition has been satisfied, transmission of the PTIME pause frame is
canceled, and only the 0 pause frame is transmitted. Depending on the interval at which the condition occurs,
however, the 0-pause frame is transmitted two times.
There is no measure to avoid this problem, such as external circuits or software. It is assumed that the system
operates without problem because the pause frame is transmitted singly or successively in the condition that is
satisfied last.
(3) Recovery from hang-up of reception/transmission
If transmission or reception is forcibly stopped because of disconnection of the cable or other reasons, the PHY
device may generate the MII signal at a timing not rated. If this happens, the
µ
PD98431 malfunctions and can no
longer execute transmission or reception. If transmission or reception freezes for these reasons, only the port in
which the problem has occurred can be recovered by the following steps:
<1>
Detect operation status.
By using the link signal of the PHY device, detect stoppage of transmission or reception.
<2>
Disable transmission or reception.
Disable reception of a new packet by clearing the SRXEN bit of the MACC1 register to 0.
Disable writing of a new packet from the high-end system.