83C694 Datasheet, PDF (17/33 Pages) List of Unclassifed Manufacturers – TWISTED PAIR INTERFACE AND MACHESTER ENCODER/DECODER

83C694D
PIN DESCRIPTION
PIN
NUMBER
32, 33,
34, 35
36
37
38
39
40
41
42
MNEMONIC SIGNAL NAME
VCC
Positive Supply
NC
TST
BSR
Not Connected
Test Input
Bias Resistor
RX-
AUI Receive
RX+
CD-
CD+
AUI Collision
I/O
DESCRIPTION
Pin 32 is positive supply to the VCO. Pin 33
is positive supply for digital and transmit cir-
cuits. Pin 34 is positive supply for digital cir-
cuits. Pin 35 is positive supply for receive
circuits.
Do not connect to this pin.
I This pin must be tied low.
I A resistor from BSR to VCC sets the internal
bias levels. Nominal value is 10KΩ 1% resis-
tor connected externally to +5V. If BSR is tied
low, a low power mode is enabled and trans-
mit/receive is disabled.
I In AUI mode, the Manchester encoded data
from an external transceiver is received on
RX+/RX-. After timing recovery and decoding,
it is output to the controller on RXD. With the
standard 78Ω transceiver AUI cable, the dif-
ferential input must be externally terminated.
This requirement can be satisfied by connect-
ing two 39.2Ω 1% resistors in series with an
optional 0.1 µF common mode bypass ca-
pacitor as shown in Figure 2-3. Matched ca-
pacitors can also be added to protect the
inputs from external faults.
I In AUI mode, a 10 MHz collision presence
signal from an external transceiver is received
on CD+/CD-. The COL pin is then output high.
The collision differential inputs, CD+ and CD-,
must be terminated in the same manner as
the receive inputs, RX+ and RX-. See Figure
2-3 for information on this design.
TABLE 3-1. PIN DESCRIPTION cont.
14