Data Sheet

4-Level FSK Modem Data Pump Page 34 of 47 MX919B PRELIMINARY INFORMATION

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Note: during this time the µC may

perform other functions, as the

µC variable 'STATE' is updated

by the interrupt service routine

Disable µC's MX919B Rx Interrupt Service Routine

Enable µC's MX919B Rx Interrupt Service Routine

Set µC variable 'STATE' to 0

Set the Mode Register IRQEN bit to '1'

Set the Mode Register IRQEN bit to '0'

Read the Status Register

Write a RESET task to the Command Register

Ensure that the Control Register

has been loaded with suitable

CKDIV, FSTOL, LEVRES and PLLBW values

Wait until the received carrier has been present

for at least 8 symbol times

Write a SFSH task to the Command Register

with the AQSC and AQLEV bits set to '1'

Ensure that the Mode Register IRQEN,

PSAVE, RXEYE and TX/RX bits are '0',

and the INVSYM bit is set appropriately

Ye s

END

with error

END

START

'STATE' < 3 ?

BFREE bit = 1 ?

'STATE' = 3 ?

Figure 21: Receive Frame Example Flowchart, Main Program

Notes

1. The RESET command in Figure 21 and the practice of disabling the MX919B’s

IRQ output when not

needed are not essential but can eliminate problems during debugging and if errors occur in operation.

2. The CRC and TXIMP bits should be set appropriately every time a byte is written to the Command