Toshiba Strata AirLink Installation Manual page 71

Timing and Synchronization
To comply with FCC part 15D clock and frame synchronization requirements, the clock and frame
frequency accuracy must be ± 10 parts per million (ppm). To meet this requirement without adding
cost, the system uses the Strata DK system as the primary clock source. The analog, digital, and
Stratum 3 trunks were considered as possible configurations.
To continue using only one single interface between the RWIU and the Base Stations, the clock
signal is sent through the E1 interface using a 320 ms synchronization pulse. The Base Stations
lock onto the RWIU clock signal and the Portable Unit Board (PUB) extracts the clock from the
Base Stations. The RWIU provides a signal to all other PCBs for a simple insertion into the E1
time slot 17.
Backplane Interface Connector
The RWIU has a 44-pin Deutsche Institut fur Normung (DIN) connector (P1) that connects to the
backplane of the Strata DK system. The connector has two rows with 22 pins in each row.
PBX Data Highway Interface
The PBX data highway control channel uses an integrated UART controller running at 312.5 kbs.
The control channel uses the following signals that originate from the backplane connector P1:
o DHOUT - receive signal (input) and connects to RX
o DHIN - transmit signal (output) and connect to TX
The UART debug serial channel connects to the integrated serial channel N0, and the
asynchronous multi-drop communication channel connects to serial channel N1. The UART
internal serial channels connect to the debug serial channel and the asynchronous multi-drop
communication channel. The debug serial channel connects to N0, and the asynchronous multi-
drop communication channel connects to the external UART device.
An RS-485 asynchronous multi-drop communication link between the RWIU and the WWIS
occurs because the UART connects to the CPU external bus. The UART is not physically mounted
on the RWIU, but uses the 28-inch PLCC socket on the RWIU.
The UART receives its operating frequency from the output of the internal timer N0 of the CPU.
N0 is programmed to divide the internal 25 MHz operating frequency of the CPU by a factor of 5
to obtain the UART 5 MHz operating frequency. It is possible to use N0 for other software
applications by substituting an optional external 5 MHz crystal.
Base Station Interface Connectors (E1s)
Four identical long-haul E1 (2048 kbs) PCM interfaces connect the RWIU PCB to each Base
Station (N0~N3) using a standard pulse (see
o Primary access transceiver devices
o Two elastic buffers for each E1 channel
o RX and TX line transformers with protectors
320 ms synchronization signal insertion logic (channel N17)
o
o Loop back controls
o RWIU generated Base Station reset (relays K1~K4)
o RFI protectors (common mode chokes - optional)
Electronic circuit breakers for each E1 channel
o
Strata AirLink Installation Guide
Table
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20). Each interface has:
RWIU System Installation
RWIU Additional Information
61