GMSK Modem Data Pump
Page 27 of 37
MX909A PRELIMINARY INFORMATION
START
Wait for IRQ line
Wait for IRQ line
Write Task = RESET
to Command Register
to go low then
to go low then
execute Rx I.S.R.
execute Rx I.S.R.
Write PLLBW, LEVRES,
DARA, and CKDIV values
to Control Register
Yes
Wait 12 Bit Periods
CRCFEC = '1' ?
A
No
Write IRQEN = '1',
SCREN = '1', TXRX = '0’
to Mode Register
Write Task = SFH
to
Command Register
Log "nth block in error"
in µC
Wait for IRQ line
to go low then
Read 18 bytes of
data from
Data Carrier Detected
Wait 2 Bit Periods
execute Rx I.S.R.
Data Buffer
µC
Read MO/BA and
CRCFEC bits from
Status Register
Yes
B
expect Mobitex
Data Block?
No
A
Write
2 Frame Sync Bytes
to Data Buffer
Read 2 Byte
Frame Head from
Data Buffer
µC expect new
Frame Head
Yes
B
No
Write Task = RDB
to
Command Register
Write Task = LFSB,
AQLEV = '1', AQBC = '1'
to Command Register,
FINISH
Rx Interrupt Service Routine
(I.S.R.)
Read Status Register
No
IRQ bit = '1' ?
Service other interrupts
Yes
DIBOVF = '1' ?
No
Yes
No
Fault detected:
Abort reception
Fault detected:
Abort reception
BFREE = '1' ?
Yes
Figure 15: Receive Process Flow Chart
¤2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480134.005
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CMLMICRO [ CML MICROCIRCUITS ]
