mc68194 ON Semiconductor, mc68194 Datasheet - Page 17

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

7.1 OVERVIEW
Request Channel and the Physical Data Indication Channel.
The serial interface is used to pass commands and data
frames to and from the CBM.
7.2 PHYSICAL DATA REQUEST CHANNEL
Three of these signals (TXSYM2, TXSYM1 and TXSYM0)
are multiplexed and have different meanings depending on
the mode of SMREQ*. When SMREQ* is equal to one, the
MAC mode is selected. When SMREQ* is equal to zero, the
physical layer management mode is selected.
7.2.1 TXCLK — Transmit Clock
TXSYM1, TXSYM0 and SMREQ* are synchronized to
TXCLK. The IEEE 802.4 standard for carrier band allows
for 5.0 or 10 MHz clocks.
7.2.2 SMREQ* — Station Management Request
physical layer management mode. In MAC mode SMREQ*
= 1 and in management mode SMREQ* = 0.
7.2.3 TXSYM0, TXSYM1, and TXSYM2 — Transmit
TXSYM1 and TXSYM0 have the meanings shown in
Figure 7−1.
commands (RESET, LOOPBACK DISABLE, ENABLE
TRANSMITTER and IDLE) encoded on lines TXSYM2,
TXSYM1 and TXSYM0. The CBM does not support the
SMDATA commands, but responds with a “NACK”. In
MAC mode, the encoding for TXSYM2, TXSYM1, and
TXSYM0 are shown in Figure 7−2.
Where:
Figure 7−2. Request Channel Encoding For MAC Mode
State
RESET
DISABLE LOOPBACK
ENABLE TRANSMITTER
SERIAL SM DATA/IDLE
Symbol
ZERO
ONE
NON−DATA
PAD−IDLE
SILENCE
Figure 7−1. Request Channel Encoding for Physical
The serial interface is composed of the Physical Data
Five signals comprise the physical data request channel.
The transmit clock can be from 1.0 to 10 MHz. TXSYM2,
SMREQ* directs the physical layer to be in MAC or
In physical layer management mode TXSYM2,
The CBM supports only four station management
ZERO is binary zero.
ONE is binary one.
NON−DATA is a delimiter flag and is always present in pairs.
PAD−IDLE is one symbol of preamble/interframe idle.
SILENCE is silence or no signal.
Management Mode (SMREQ* = 0)
(SMREQ* = 1)
Symbols
TXSYM2
TXSYM2
1
1
0
0
0
0
1
0
1
TXSYM1
TXSYM1
SECTION 7 − SERIAL INTERFACE
1
0
1
0
0
0
0
1
1
TXSYM0
TXSYM0
http://onsemi.com
0/1
X
X
X
1
1
1
0
1
17
7.3 PHYSICAL DATA INDICATION CHANNEL
channel. Three of these signals (RXSYM2, RXSYM1 and
RXSYM0) are multiplexed and have different meanings
depending on the state of SMIND*. When SMIND* is equal
to one, the physical layer is in MAC mode and when
SMIND* is equal to zero, the physical layer is in
management mode or an error has occurred.
7.3.1 RCXLK — Receive Clock
RXSYM1, RXSYM0, and SMIND* are synchronized to
RXCLK. The IEEE 802.4 standard for carrier band
networks allows 5.0 or 10 MHz clocks.
7.3.2 SMIND* — Station Management Indication
mode (SMIND* = 1) or management mode (SMIND* = 0)
of operation. When in MAC mode of operation, the physical
layer has RXSYM2, RXSYM1, and RXSYM0 encoded
indicating data reception. When in management mode of
operation, the physical layer RXSYM2, RXSYM1 and
RXSYM0 are encoded to confirm response to received
commands or to indicate a physical error (jabber inhibit).
7.3.3 RXSYM0, RXSYM1 and RXSYM2 — Receive
physical management mode is shown in Figure 7−3:
MAC mode is shown in Figure 7−4.
Where:
*Indicates RXSYM0 contains the SM RX data when responding to a serial
Figure 7−3. Indication Channel Encoding For Physical
State
NACK (non−acknowledgement)
ACK (acknowledgement)
IDLE
Physical Layer Error
data command.
Symbol
ZERO
ONE
NON−DATA
SILENCE
BAD SIGNAL
Five signals comprise the physical data indication
The receive clock can be from 1.0 to 10 MHz. RXSYM2,
SMIND* indicates whether the physical layer is in MAC
The encoding for RXSYM2, RXSYM1, and RXSYM0 in
The encoding of RXSYM2, RXSYM1, and RXSYM0 in
ZERO is the received data zero.
ONE is the received data one.
NON−DATA is a delimiter flag and is always present in pairs.
SILENCE is silence or no signal.
BAD SIGNAL is received bad signal.
X = Don’t care.
Figure 7−4. Indication Channel Encoding For MAC
Management Mode (SMIND* = 0)
Mode (SMIND* = 1)
Symbols
RXSYM2
RXSYM2
0
0
1
1
0
1
0
0
1
RXSYM1
RXSYM1
0
0
0
1
1
0
1
0
1
RXSYM0
RXSYM0
X
X
X
0
1
1
1
*
*