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componentes Descripción

Fabricante

MC68194
(Rev.:2006)

Carrier Band Modem (CBM)

ON Semiconductor 

MC68194

SECTION 2

SIGNAL DESCRIPTION

Symbol

TXSYM0−TXSYM2

SMREQ*

TXCLK

RXSYM0−RXSYM2

SMIND*

RXCLK

EOTDIS*

TXOUT,TXOUT*

TXDIS

JAB

RESET

Type Name/Description

TTL/I*

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.

TTL/I*

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.

TTL/O

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.

TTL/O

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.

TTL/O

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.

TTL/O

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.

TTL/I*

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.

ECL/O TRANSMIT OUTPUTS — A differential output signal pair (MECL level referenced to

VCC) used to drive the transmitter circuitry. The silence or “off” state is both outputs one

(high). The output data stream is phase−coherent FSK encoded.

OC 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).

TTL/O 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.

TTL/I* RESET — A TTL input signal that when high asynchronously resets the CBM.

*All TTL inputs include a 15 kΩ pullup resistor to VCC.

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