CMX989 Datasheet, PDF (7/31 Pages) CML Microcircuits – CDPD MAC and Data Pump Processor

CDPD MAC and Data Pump Processor
CMX989
1.5 General Description
This device performs the data encapsulation and synchronisation functions of the Medium
Access Control (MAC) layer part of the CDPD specification, as well as the generation of
baseband signals in the physical layer, all of which are specifically for the Mobile End Station (M-
ES). For details of the system requirements and telegram formats, the user is referred to
“Cellular Digital Packet Data System Specification” (Release 1.1), Volumes 1 to 5, currently
available from:
CDPD Industry Input Coordinator
Cellular Digital Packet Data System Specification
650 Town Center Drive, Suite 820
Costa Mesa, CA 92626
United States of America
1.5.1
Principles of Operation
The CMX989 functions (as shown in the block diagram of Figure 1) may be accessed and/or
controlled via memory mapped 8-bit registers connected to the host µController parallel bus
interface. Write registers allow the device to be set up, controlled and used for transmission of
data. Read registers allow received data to be read and the status of the CMX989 to be
monitored. There are several registers which can be used to assist end-product manufacture and
test and related system test.
It is assumed that many applications will be assisted by the use of interrupt routines, so various
functions within the device will cause a hardware interrupt, eg: when received data is available to
be read or space is available to write data for transmission. Each hardware interrupt source may
be individually disabled (masked) or enabled. The interrupt pin (IRQN) is reset high by a read of
either IRQ FLAGS or IRQ FLAGS 2 registers and the bits read from these registers and the
STATUS register reflect the status of the CMX989 at the time the read is performed. The IRQ
FLAGS, IRQ FLAGS2 and STATUS registers can be polled (without the use of a hardware
interrupt routine call) if this is preferred.
For reference, the structures of the Reverse and Forward Channel transmissions are shown in
Figures 3 and 4.
© 2001 Consumer Microcircuits Limited
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