mc68194 ON Semiconductor, mc68194 Datasheet - Page 7

• Manufacturer Part Number: mc68194
• Description: Carrier Band Modem Cbm
• Manufacturer: ON Semiconductor

Symbol
TXSYM0−TXSYM2
SMREQ*
TXCLK
RXSYM0−RXSYM2
SMIND*
RXCLK
EOTDIS*
TXOUT,TXOUT*
TXDIS
JAB
RESET
*All TTL inputs include a 15 kΩ pullup resistor to V
ECL/O
TTL/O
TTL/O
TTL/O
TTL/O
TTL/O
TTL/I*
TTL/I*
TTL/I*
TTL/I*
Type
OC
Name/Description
TRANSMIT SYMBOLS — These TTL inputs are request channel signals used to send
either serial transmission symbols in the MAC mode or commands in station
management mode. They are synchronized to TXCLK and are normally connected to
the TXSYMX outputs of the MC68824. SMREQ* selects the meaning of these signals
as either MAC mode or management mode.
STATION MANAGEMENT REQUEST — A TTL input that selects the mode of the
request channel signals TXSYMX. Synchronized to TXCLK, SMREQ* is equal to one
for MAC mode and equal to zero for management mode. It is normally driven by the
SMREQ* output of the MC68824.
TRANSMIT CLOCK — A TTL clock output generated from the crystal oscillator (it is 1/4
of the oscillator frequency) used to receive request channel symbols from the MC68824.
TXCLK is equal to the data rate of the application (5.0 MHz or 10 MHz for IEEE 802.4).
TXSYMX and SMREQ* are synchronized to the positive edge of TXCLK which is
supplied to the MC68824.
RECEIVE SYMBOLS — These TTL outputs are indication channel signals used to
provide either serial receive symbols in MAC mode or command confirmation/indication
in station management mode. They are synchronized to RXCLK and are normally
connected to the RXSYMX inputs of the MC68824. SMIND* selects the meaning of
these signals as either MAC mode or management mode.
STATION MANAGEMENT INDICATION — A TTL output that indicates the mode of the
CBM and RXSYMX lines. Synchronized to RXCLK, SMIND* is equal to one for MAC
mode and equal to zero for management mode. It is normally connected to the SMIND*
input of the MC68824.
RECEIVE CLOCK — A TTL clock output used to send indication channel symbols to
the MC68824. Its frequency is nominally equal to the data rate (5.0 MHz or 10 MHz for
IEEE 802.4). RXCLK is generated from a PLL that is locked to the local oscillator during
loopback, station management, or the absence of received data. During frame reception
the PLL is locked to the incoming received data. RXSYMX and SMIND* are
synchronized to negative edge of RXCLK.
END−OF−TRANSMISSION DISABLE — When low, this TTL input disables the
end−of−transmission receiver blanking required by the IEEE 802.4 Spec, Section
12.7.6.3. When high the blanking works in accordance with the spec requirements.
TRANSMIT OUTPUTS — A differential output signal pair (MECL level referenced to
V
(high). The output data stream is phase−coherent FSK encoded.
TRANSMIT DISABLE — An open collector output used to disable transmitter circuitry.
This output is high when the transmitter is off (TXOUT and TXOUT* both high).
JABBER — A TTL output signal generated from the jabber−inhibit timer. When equal
to one, JAB indicates the timer has timed−out and an error has occurred.
RESET — A TTL input signal that when high asynchronously resets the CBM.
CC
) used to drive the transmitter circuitry. The silence or “off” state is both outputs one
CC
SIGNAL DESCRIPTION
.
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SECTION 2
7