FX919B Datasheet, PDF (16/47 Pages) CML Microcircuits – Excellent Radio Fading Performance

4-Level FSK Modem Data Pump
FX919B
Data from µC to Block Buffer
Task from µC to Command Register
BFREE bit of Status Register
IRQ bit of Status Register
IRQN o/p (IRQNEN = '1')
TXOP signal
Task 1
Task 2
from task 1
from task 2
Figure 8 Transmit Task Overlapping
When the modem is in receive mode, the µC should wait until the BFREE bit of the Status Register is '1', then
write the desired task to the Command Register.
Once the byte containing the desired task has been written to the Command Register, the modem will:
Set the BFREE bit of the Status Register to '0'.
Wait until enough received symbols are in the De-interleave Buffer.
Decode them as needed, and transfer the resulting binary data to the Data Block Buffer
Then the modem will set the BFREE and IRQ bits of the Status Register to '1', (causing the IRQN
output to go low if the IRQNEN bit of the Mode Register has been set to '1') to tell the µC that it may
read from the Data Block Buffer and write the next task to the modem. If more than 1 byte is contained
in the buffer, byte number 0 of the data will be read out first.
In this way the µC can read data and write a new task to the modem while the received symbols needed for this
new task are being received and stored in the De-interleave Buffer.
RXIN signal
IRQN o/p (IRQNEN = '1')
IRQ bit of Status Register
for task 1
BFREE bit of Status Register
Task from µC to Command Register
Data from Block Buffer to µC
Task 1
Figure 9 Receive Task Overlapping
Detailed timings for the various tasks are given in Figures 10 and 11.
for task 2
Task 2
Task 1 data
© 1997 Consumer Microcircuits Limited
16
D/919B/1