CMX969P4 查看數據表（PDF） - MX-COM Inc

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CMX969P4

MOTIENT/ARDIS RD-LAP MDC4800 Modem

MX-COM Inc  

MOTIENTSM/ARDISSM RD-LAPTM MDC4800 Modem

15

CMX969 Advance Information

4.5.4.1 Command Register B7: AFSD - Autonomous Frame Sync Detect

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 Command Register B6: RXEYE - Show Rx Eye

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.

Figure 7: Ideal 'RXEYE' Signal: RD-LAP Mode

In MDC mode the eye diagram should be as shown in Figure 8.

Figure 8: Ideal 'RXEYE' Signal: MDC Mode

4.5.4.3 Command Register B5-3

These bits are reserved for future use and should always be set to ‘0’.

4.5.4.4 Command Register B2, B1, B0: TASK

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.

www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054

Doc. # 20480211.002

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

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