GMSK Packet Data Modem and RF Transceiver
CMX990
Task Timings
The device should not write to the Command Register whenever the Enable Baseband bit is
changed from ‘0’ to ‘1’ and for at least 2 bit times after the following:
Changing the Tx/Rx bit.
Resetting or after power is applied to the device.
This is to ensure that the internal operation of the device is initialised correctly for the new task.
Note that this only applies to the Command Register, the other registers may be accessed as
normal.
Figure 14 Transmit Mode Timing Diagram
Task
Typical time
(bit-times)
Time from writing first task (modem in ‘idle’
state) to application of first transmit bit to Tx
Low Pass filter
Time from application of first bit of
task to Tx Low Pass filter until BFREE
goes to a logic ‘1’ (high)
t1
t2
Any
1
T7H
TQB
TDB
TSB
TSD
36
24
20
1
6
Time to transmit all bits of task
T7H
TQB
TDB
TSB
TSD
56
32
240
8
t3
t4
72
Max time allowed from BFREE going to a
logic ‘1’ (high) for next task (and data) to
be written to modem
T7H
TQB
TDB
TSB
TSD
18
6
218
6
64
ã 2004 CML Microsystems Plc
28
D/990/1
CMLMICRO [ CML MICROCIRCUITS ]
