CMX868E2 View Datasheet(PDF) - MX-COM Inc
Part Name
Description
MFG CO.
'CMX868E2' PDF : 43 Pages View PDF
Low Power V.22bis Modem
27
CMX868 Advance Information
Decoding of Status Register b8,7 in Rx Modem Modes, see also Figure 14.
b8 b7
11
10
01
00
De-scrambler disabled
-
Unscrambled 0s
Unscrambled 1s
-
De-scrambler enabled (DPSK/QAM modes only)
Scrambled 1s
Scrambled 0s
Unscrambled 1s
-
When the descrambler is enabled then detection of continuous unscrambled 1s will inhibit the continuous
scrambled 1s detector.
Rx signal
Status Register bit 5,6,7,8,9 or 10
Detect time
Status Register bit 15 (IRQ)
Note 1
Hold time
Note 3
IRQ output
Note 2
Notes: 1. IRQ will go high only if appropriate IRQ Mask bit in General Control Register is set.
The IRQ bit is cleared by a read of the Status Register.
2. IRQ output will go low when IRQ bit high if IRQEN bit of General Control Register is set
3. In Rx Modem modes Status Register bits 5 and 6 are set by a Rx Data Ready or
Rx Data Underflow event and cleared by a read of the Rx Data Register
Figure 17: Operation of Status Register bits 5-10
The IRQ output pin will be pulled low (to VSS) when the IRQ bit of the Status Register and the IRQ EN bit
(b6) of the General Control Register are both 1.
Changes to Status Register bits caused by a change of Tx or Rx operating mode can take up to 150Ps to take
effect.
In Powersave mode or when the Reset bit (b7) of the General Control Register is 1 the Ring Detect bit (b14)
continues to operate but all other bits will be 0.
The ‘continuous 0’ and ‘continuous 1’ detectors monitor the Rx signal after the QAM/DPSK descrambler, (see
Figure 14) and hence will detect continuous 1s or 0s if the descrambler is disabled, or continuous scrambled
1s or 0s if the descrambler is enabled.
In QAM or DPSK Rx modem modes b2-0 of the Status Register contain a value indicative of the received
signal BER, see Figure 19. In Rx FSK modem modes bits 2 and 1 will be zero and b0 will show the output of
the frequency demodulator, updated at 8 times the nominal data rate.
¤2001 MX-COM, Inc.
www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480205.007
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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