MB86961A Datasheet, PDF (12/29 Pages) Fujitsu Component Limited. – UNIVERSAL INTERFACE FOR 10BASET

MB86961A
TRANSMIT FUNCTION
The MB86961A receives NRZ data from the controller at
the TXD input (see MB86961A block diagram), and
passes it through a Manchester encoder. The encoded
data is then transferred to either the AUI cable (the DO
circuit) or the twisted-pair network (the TPO circuit). The
advanced integrated pulse shaping and filtering network
produces the output signal on TPON and TPOP, shown in
Figure 6. The TPO output is pre-distorted and prefiltered
to meet the 10BASE-T jitter template. No external filters
are required. During idle periods, the MB86961A trans-
mits link integrity test pulses on the TPO circuit if LI is
enabled and integrated PLS/MAU mode is selected. The
MB86961A can be programmed for either shielded TP
(150 Ω) or unshielded TP (100 Ω) through the UTP pin.
JABBER CONTROL FUNCTION
Figure 7 is a state diagram of the MB86961A Jabber con-
trol function. The MB86961A on-chip watchdog timer
prevents the DTE from locking into a continuous transmit
mode. When a transmission exceeds the time limit, the
watchdog timer disables the transmit and loopback func-
tions, and activates the JAB pin. Once the MB86961A is
in the jabber state, the TXD circuit must remain idle for a
period of 0.25 to 0.75 seconds before it will exit the jab-
ber state.
SQE FUNCTION
In the integrated PLS/MAU mode, the MB86961A sup-
ports the signal quality error (SQE) function as shown in
Figure 8. After every successful transmission on the
10BASE-T network, the MB86961A transmits the SQE
signal to the DTE for 10 ±5 bit times over the internal CI
Circuit.
RECEIVE FUNCTION
The MB86961A receive function acquires timing and
data from the twisted-pair network (the TPI circuit) or
from the AUI (the DI Circuit). Valid received signals are
passed through the on-chip filters and Manchester
decoder and output as decoded NRZ data and receive tim-
ing on the RXD and RCLK pins, respectively. No exter-
nal filters are required.
An internal intelligent squelch function discriminates
noise from link test pulses and valid data streams. The
receive function is activated only by valid data streams
above the squelch level and with proper timing. If the dif-
ferential signal at the TPI or the DI circuit inputs falls
below 75% of the threshold level (unsquelched) for eight
bit times (typical), the MB86961A receive function enters
the idle state. If the polarity of the TPI circuit is reversed,
the MB86961A detects the polarity reversal and reports it
via the PLR output. The MB86961A automatically cor-
rects reversed polarity.
POLARITY REVERSE FUNCTION
The MB86961A polarity reverse function uses both link
pulses and end-of-frame data to determine the polarity of
the received signal. A reversed polarity condition is
detected when eight opposite receive link pulses are
detected without receipt of a link pulse of the expected
polarity. Reversed polarity is also detected if four frames
are received with a reversed start-of-idle. Whenever
polarity is reversed, these two counters are reset to zero.
If the MB86961A enters the link fail state and no valid
Power On
NO OUTPUT
(DO = Active)
NONJABBER OUTPUT
Start_XMIT_Max_Timer
(DO = Idle)
(DO = Active)•
(XMIT_Max_Timer_Done)
JAB
XMIT = Disable
LPBK = Disable
CI = SQE
(DO = Idle)
UNJAB WAIT
Start_Unjab_Timer
XMIT = Disable
LPBK = Disable
CI = SQE
Figure 6. MB86961A TPO Output Waveform
(Unjab_Timer_Done)
(DO = Active)
(Unjab_Timer_Not_Done)
Figure 7. Jabber Control Function
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