Renesas R-IN32M3 Series User Manual page 164

R-IN32M3-EC User's Manual
7.2.4 Fast Link-Loss Detection Function
It is possible to generate the interrupt as soon as possible or bring down the link by monitoring the state of the
communication when the communication is poor. Two functions with BER monitor and FEQ monitor are available.
(1) BER Monitor
The bit error rate (BER) monitor function can be used to measure the bit error of specific time, count the number of
errors and notify. When the threshold is exceeded, it can link down as a trigger and inform the CPU by generating an
interrupt signal. Element to be an error is different in the IDLE state and data communication as follows.
⚫ In the IDLE state when communication is not performed, count the error judged as bit error when received symbol
is other than IDLE symbol or J symbol which means the start of frame. Error count is only one when continuous
error symbols without normal symbols are received.
⚫ When the communication is performed, count the error judged as bit error when received symbol is other than
data code group, IDLE code group or control code group in 32 kinds of symbols. Error count is up whenever error
symbol is received.
The operation of the BER monitor function is done by register 23 and as shown below.
The first step is to check whether the port is in the link state by reading BER_LNK_OK. Note that the port does not work
properly in the link-down state. Set the BER_CNT_LNK_EN, BER_CNT_TRIG, and BER_WINDOW parameters once
the link state is verified. The error detection function starts to operate by writing 0 to BER_WINDOW. An interrupt is
generated when the number of errors exceeding the threshold is detected within the specified time in the BER_WINDOW.
When using the interrupt, release the interrupt mask by writing 1 to bit 10 in register 30 before setting the said parameters.
To end the operation of BER function, write 0 to BER_WINDOW. When an interrupt was used, mask the interrupt by
writing 0 to bit 10 in register 30.
(2) FEQ Monitor
To stably receive the incoming data, optimization is done by filtering the incoming signal by DSP in the PHY. FEQ is the
coefficients of this filter and the value fluctuates greatly when the amplitude of the signal being received is changed. It
can output the interrupt when detecting variation that exceeds the threshold set in advance or link down by monitoring
the variation.
The operation of the FEQ monitor function is done by register 24 and as shown below.
Firstly, set the variation to be detected in FEQ_DELTA. The reference value at the time of writing can be referred by
writing 0xfffe to FEQ_DELTA and reading FEQ_VAL. FEQ monitor function will begin to work when the threshold of
variable of FEQ_DELTA is set. Current value of FEQ monitor can be detected by reading FEQ_VAL. An interrupt is
generated when the value of FEQ_VAL exceeds the threshold. When using the interrupt, release the interrupt mask by
writing 1 to bit 9 in register 30 before setting the said parameters. To end the operation of FEQ function, write 0xFFFF to
FEQ_DELTA. When an interrupt was used, mask the interrupt by writing 0 to bit 9 in register 30.
R18UZ0003EJ0501
Jan. 12, 2021
7. Ethernet PHY Function
Page 151 of 224