4-Level FSK Modem Data Pump
Page 5 of 50
MX929B PRELIMINARY INFORMATION
Figures
Figure
Page
Figure 1: Block Diagram ................................................................................................................................... 6
Figure 2: Recommended External Components .............................................................................................. 8
Figure 3: Typical Modem
PC
connections ...................................................................................................... 10
Figure 4: Translation of Binary Data to Filtered 4-Level Symbols in Tx Mode................................................ 11
Figure 5: RRC Filter Frequency Response vs. Bit Rate (including the external RC filter R4/C5) .................. 12
Figure 6: RRC Filter Frequency Response vs. Symbol Rate (including the external RC filter R4/C5)........... 12
Figure 7: Over-Air Signal Format.................................................................................................................... 15
Figure 8: Alternative Frame Structures........................................................................................................... 16
Figure 9: Transmit Task Overlapping ............................................................................................................. 18
Figure 10: Receive Task Overlapping ............................................................................................................ 19
Figure 11: Transmit Task Timing Diagram ..................................................................................................... 23
Figure 12: Receive Task Timing Diagram ...................................................................................................... 23
Figure 13: RRC Low Pass Filter Delay ........................................................................................................... 23
Figure 14: Ideal 'RXEYE' Signal ..................................................................................................................... 27
Figure 15: Typical Data Quality Reading vs S/N............................................................................................. 29
Figure 16: Input Signal to RRC Filter in Tx Mode for TXIMP = 0 and 1 ......................................................... 31
Figure 17: Tx Signal Eye TXIMP = 0 .............................................................................................................. 31
Figure 18: Tx Signal Eye TXIMP = 1 .............................................................................................................. 32
Figure 19: Transmit Frame Example Flowchart, Main Program .................................................................... 34
Figure 20: Tx Interrupt Service Routine.......................................................................................................... 35
Figure 21: Receive Frame Example Flowchart, Main Program....................................................................... 37
Figure 22: Rx Interrupt Service routine........................................................................................................... 38
Figure 23: Acquisition Sequence Timing ........................................................................................................ 39
Figure 24: Effect of AC Coupling on BER (without FEC)................................................................................ 40
Figure 25: Decay Time - AC Coupling ............................................................................................................ 41
Figure 26: Typical Connections between Radio and MX929B ....................................................................... 42
Figure 27: Received Signal Quality Monitor Flowchart ................................................................................... 43
Figure 28:
PC
Parallel Interface Timings ........................................................................................................ 47
Figure 29: Typical Bit Error Rate With and Without FEC ............................................................................... 48
Figure 30: 24-pin SOIC Mechanical Outline:
Order as part no. MX929BDW
................................................ 49
Figure 31: 24-pin SSOP Mechanical Outline:
Order as part no. MX929BDS................................................
49
Figure 32: 24-pin PDIP Mechanical Outline:
Order as part no. MX929BP
.................................................... 50
©2001 MX-COM, INC.
www.mxcom.com Tel: 800 638 5577 336 744 5050
Fax: 336 744 5054
Doc. # 20480171.003
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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