MC68181
Flex chip System Design
MOTOROLA
MC68181P/D, Preliminary
3
PRELIMINARY
When first acquiring a FLEX signal, the receiver is stepped through frequencies in the scan list,
and the signal checked for FLEX information. The Roaming software checks the Network
Identifier (NID) and Simulcast System Identifier (SSID), to determine the correct channel(s) to
lock onto. During idle frames, other channels may be scanned for the presence of FLEX signals
and alternate channels. FLEXstack software also captures Traffic Management Flags, assisting
load management by shifting groups of subscribers between channels.
FLEX PROTOCOL
FLEX System Software from Motorola is a family of software components for building world-
class products incorporating messaging capabilities. FLEXstack Software is specifically
designed to support the FLEX chip IC. It runs on a product’s host processor and communicates
with the FLEX chip IC, fully controlling the receiver subsystem and interpreting the code words
that are passed to the host from the FLEX chip IC.
FLEX protocol offers more than 10 times the data capacity of a POCSAG 512 bps system, and at
least 12 times the fading protection. FLEX protocol operates at 1600, 3200, and 6400 bps, allowing
a system to increase capacity as demands increase, without replacing or reconfiguring the pager
units. FLEX protocol is synchronous—all data intended for a particular pager is scheduled in
pre-defined time slots, so the receiver and host processor are only active when messages are
scheduled for delivery.
ROAMING FLEX PROTOCOL
Roaming FLEX provides the ability to tune the receiver circuits into the required paging channel.
This allows roaming in areas serviced by transmitters using different frequencies, or load
balancing and reallocating where multiple frequencies are used to serve a single area.
Figure 2
Roaming FLEX Receiver Block Diagram
LNA
MC3374
MC13150
Mixer/Amp
MMBR961LT1
MR947T1
MC13143
Data
Frequency
Synthesizers
SPI
MRF1047T1
MRF927T1
MRF947T1
MRFIC0916
MRFIC0915
MRF947T1
MRF927T1
MRF2947AT1
MC141592
MC68181FDB
FLEX
TM
Subsystem
MC68181
FSK RF In
2/4 level
Rec
Audio
AA1216
MC68HC08
MC68HC11/12
MC68328
MPC821
DSP56L811
2-bit
FM IF
ADC
SPI
PLL
VCO/Buffer
Host
Processor
IF STAGES
FLEX
TM
A/O