CMX980AL7 CML Microcircuits, CMX980AL7 Datasheet - Page 54

• Manufacturer Part Number: CMX980AL7
• Description: TETRA Baseband Processor
• Manufacturer: CML Microcircuits

TETRA Baseband Processor
Title:
Address:
Function:
Description:
7:3
Bit
2
1
0
1999 Consumer Microcircuits Limited
SyncStep
SyncInc
Enable_Change
SymClkPhase
Transmit Symbol Clock Phase adjustment register
$0x24
RW
Allows phase adjustment of the internal symbol clock reference phase with respect to system
time.
synchronised initially to the N_RESET signal. To allow correction or adjustment of this phase,
without recourse to chip reset, a mechanism is provided via this register to advance or retard
the phase of the symbol clock. The adjustment can be done in steps of ñ 1/4 or ñ 1/8 of a symbol
time. The ñ 1/4 step complies with the TETRA requirement on phase adjustment with respect
to the BS.
To ensure that the symbol clock phase is adjusted at the correct time and only in the step sizes
allowed an interlock mechanism is used. The operation to alter the phase involves two write
commands to the SymClkPhase Register in succession. The first can be considered as an
“arm” write operation and the second as the execute. The execute write must occur before the
next symbol clock as this signal cancels any “arm” state that is pending.
The simplest way is to time the “arm” write after the symbol clock strobe is detected on the
N_IRQ pin, then followed immediately by the execute write.
If detection of the N_IRQ is not desired then three successive writes guarantee that the change
will take place.
Name
The CMX980A symbol clock is a division of the Master clock frequency and is
High
Active State
RW
RW
RW
RW
54
This determines the phase advance/retard step
size.
This determines whether the operation is an
advance or retard step
1: Advance the phase by step size
0: Retard the phase by step size
The handshake and phase change enable bit. It is
set by the user and cleared by the next internal
symbol clock.
Reserved. These bits should be set Low.
Undefined on read.
1: ñ 1/4 symbol change
0: ñ 1/8symbol change
Function
CMX980A
D/980A/3