MC68175
Flex Protocol
MOTOROLA
MC68175P/D, Preliminary
3
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 FLEXchip IC. FLEXstack Software runs on a product’s
host processor and takes care of communicating with the FLEXchip IC and fully interpreting
the code words that are passed to the host from the FLEXchip IC.
FLEX protocol can give the service provider a capacity increase of greater than 10 times over
a POCSAG 512 bps system. FLEX protocol can operate at three different speeds, allowing a
system to initially run more slowly, and then increase speed as system demands increase,
while still using the same pager units. FLEX protocol provides accurate message delivery by
offering protection from fading conditions, such as bridges or overpasses. It provides 12
times the fading protection of POCSAG 1200, and 24 times the fading protection of POCSAG
2400. FLEX protocol is a synchronous time slot scheme, designed to increase the battery life
of pagers. Instead of sending out messages at random, all paging data intended for a
particular pager is scheduled into a pre-defined time slot. This allows a FLEX pager to
selectively decode one or more frames over each four minute FLEX cycle, so that the pager
does not waste its battery life decoding data intended for other pagers.
Figure 2
FLEXchip System Block Diagram
SPI
MC68175
FLEXchip
IC Decoder
A/D
Converter
Audio
38.4 kHz
Clock Out
RF
MC13141
MC13142
MMBR941
MC13150
MC3367
MC3374
MC68HC05xxHC08xx
MC68HC11/HC12/HC16xx
MC683xx/MPC5xx/8xx
API
FLEXstack
Software
Data
Ready
Receiver
Control
76.8 kHz
Oscillator
Analog to
Digital
Converter
User
Interface
LNA
IF
Host
Microprocessor
AA0814