Service Manual

GSM-204-323
MCUF
31st Oct 01
Technical Description: Horizon macro outdoor
68P02902W02-A
CONTROLLED INTRODUCTION
Tech. 6–13
Phase lock loop (PLL) operating modes
The PLL uses the selected reference signal as the loop reference clock. It
includes an OCXO accurate to 0.05 ppm, a phase comparator and a loop filter.
The PLL has the following operating modes:
 Warm-up
The PLL is open loop and using the calibration frequency, but the OCXO
is not yet warmed up.
 Set frequency
The PLL is open loop and using the calibration frequency, and the OCXO
is warmed up.
 Fast tune
Closed loop with wide filter for coarse locking to the reference (extracted
from network clock).
 Fine tune
Closed loop with narrow filter for accurate locking to the reference
(extracted from network clock).
When in fine tune closed loop mode, the accuracy is 0.01 ppm.
Sync block code load
The sync block controller has a dedicated 2.048 Mbit/s serial link into the ASIC
enabling a 64 kbit/s HDLC channel to the main processors for code loading.
The sync block includes 256 kbytes of flash EPROM, which is used to store:
 Boot code.
 Operational code.
The boot code, which cannot be altered, queries the main processors on the
current version of the sync operational code.
If the stored operational code is the correct version, the boot code will move the
operational code to RAM and execute the code.
If the query results in the need for new operational code, the sync processor will
download the operational code from the main processors via the ASIC to the
RAM in the sync block.
After a successful download, the boot code programmes the flash EPROM with
the new operational code and runs the operational code in RAM.
GSM counters
The following counters are provided:
 GSM frame incremented every 4.615 ms; range 0 - 1325.
 GSM superframe incremented every 6.12 s; range 0 - 2047.