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CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
60
Table 3-7. Setting of Mirror Port 4
Mirror Port
[P4EN = 1]
Port Selection
MP4[1:0]
Transmission/
Reception Selection
T/R4
Mirror Port 4 MII Output
00
0
Port 4 MII receive data
00
1
Port 4 MII transmit data
01
0
Port 5 MII receive data
01
1
Port 5 MII transmit data
10
0
Port 6 MII receive data
10
1
Port 6 MII transmit data
11
0
Port 7 MII receive data
Port 4
11
1
Port 7 MII transmit data
Caution The mirror port function can be used only when the selected port and mirror port are in MII mode
(when the EXINT bit of the PCSC register is 0).
3.15 Low-Power Mode
The
µ
PD98431 has a register, POWR, that reduces the power consumption if some ports are not used. By setting
a bit of the POWD register to 1, clock supply to the corresponding port is cut and the power consumption is reduced.
Each bit of the POWD register can be turned ON/OFF while the
µ
PD98431 is operating. The port corresponding
to the bit of the POWD register that is set to 1 enters the sleep status and is excluded from the round-robin sequence
in reception. Because the register setting before the port enters the sleep status is not held, the registers must be re-
set after the port has been released from the sleep status.
Because HCLK is not supplied to a sleeping port, the setting register of the port cannot be accessed while the port
is sleeping. Because the register setting before the port enters sleep status is not preserved, it must be set again
after sleep status has been cleared.
If sleep status is set without clearing interrupt sources, the INT# signal may remain asserted. Because the port
setting register cannot be cleared as it cannot be accessed while the port is sleeping, clear the interrupt source of the
corresponding port before setting the POWD register, and then set the port in sleep status.
To set the corresponding port in sleep status while data is read from the receive FIFO or written to the transmit
FIFO, wait until the FIFO bus operation to the port enters the IDLE status.
If sleep status is set while data is received from or transmitted to a network, the packet being received or
transmitted is canceled. Nor is the data that has been already stored to the FIFO preserved. To clear sleep status,
execute software reset after releasing sleep status (refer to
3.16 (3), (4)
for details of the software reset procedure).
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