CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 15

• Manufacturer Part Number: CMX969D5
• Description: MOTIENT/ARDIS RD-LAP MDC4800 Modem
• Manufacturer: MX-COM, Inc.

MOTIENT
4.5.4.1
Setting this bit to ‘1’ in receive mode enables the Autonomous Frame Sync Detect function. It has no effect in
transmit mode.
4.5.4.2
This bit should normally be set to '0'.
Setting it to '1' when the modem is in receive mode connects the input of the Tx output buffer to the Rx filter
output (see Figure 1). This allows the filtered and equalized receive signal to be monitored with an
oscilloscope (at the TXOUT pin itself), to assess the quality of the complete radio channel including the Tx
and Rx modem filters, the Tx modulator and the Rx IF filters and FM demodulator. In transmit mode this bit
has no effect.
In RD-LAP mode the resulting eye diagram (for reasonably random data) should ideally be as shown in
Figure 7, with 4 'crisp' and equally spaced crossing points.
In MDC mode the eye diagram should be as shown in Figure 8.
4.5.4.3
These bits are reserved for future use and should always be set to ‘0’.
4.5.4.4
Operations such as transmitting or receiving a data block are treated by the modem as 'tasks' and are
initiated when the µC writes a byte to the Command Register with the TASK bits set to anything other than
the 'NULL' code.
The µC should not write a task (other than NULL or RESET) to the Command Register or write to or read
from the Data Buffer when the BFREE (Buffer Free) bit of the Status Register is '0'.
Different tasks apply in RD-LAP and MDC receive and transmit modes.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
SM
/ARDIS
Command Register B7: AFSD - Autonomous Frame Sync Detect
Command Register B6: RXEYE - Show Rx Eye
Command Register B5-3
Command Register B2, B1, B0: TASK
SM
RD-LAP
www.mxcom.com Tel: [phone] 744 5050 Fax: [phone]
TM
MDC4800 Modem
Figure 7: Ideal 'RXEYE' Signal: RD-LAP Mode
Figure 8: Ideal 'RXEYE' Signal: MDC Mode
15
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CMX969 Advance Information
Doc. # 20480211.002