CMX969D5 MX-COM, Inc., CMX969D5 Datasheet - Page 7

• Manufacturer Part Number: CMX969D5
• Description: MOTIENT/ARDIS RD-LAP MDC4800 Modem
• Manufacturer: MX-COM, Inc.

MOTIENT
4 General Description
4.1 Description of Blocks
Refer to Figure 1.
4.1.1
Eight bi-directional 3-state logic level buffers between the modem's internal registers and the host µC's data
bus lines.
4.1.2
This block controls the transfer of data bytes between the µC and the modem's internal registers, according to
the state of the Write and Read Enable inputs ( WR and RD ), the Chip Select input ( CS ) and the Register
Address inputs A0 and A1.
The Data Bus Buffers, Address and R/W Decode blocks provide a byte-wide parallel µC interface, which can
be memory-mapped, as shown in Figure 3.
4.1.3
Two 8-bit registers which the µC can read to determine the status of the modem and the received data
quality.
4.1.4
The values written by the µC to these 8-bit registers control the operation of the modem.
4.1.5
A 12-byte buffer used to hold receive or transmit data to or from the µC.
4.1.6
A circuit which generates (in transmit mode) or checks (in receive mode) the Cyclic Redundancy Checksum
bits, which are included in transmitted data blocks so that the receive modem can detect transmission errors.
4.1.7
In transmit mode, this circuit adds Forward Error Correction information to the transmitted data. In RD-LAP
mode it also converts the binary data to 4-level symbols. In receive mode, this block translates received
symbols to binary data, using the FEC information to correct a large proportion of transmission errors.
¤ ¤ ¤ ¤ 2001 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
µCONTROLLER
SM
Data Bus Buffers
Address and R/W Decode
Status and Data Quality Registers
Command, Mode and Control Registers
Data Buffer
CRC Generator/Checker
FEC Encoder/Decoder
/ARDIS
SM
RD-LAP
www.mxcom.com Tel: [phone] 744 5050 Fax: [phone]
IRQ
TM
WR
RD
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
An
. .
. .
.
MDC4800 Modem
Figure 3: Typical Modem µ µ µ µ C Connections
µC Data Bus
µC Address Bus
. .
. .
.
V
DD
IRQ pull up
All trademarks and service marks are held by their respective companies.
7
resistor
. .
. .
.
Address
Decode
Modem
other
to µController
IRQ
inputs
CMX969 Advance Information
D0
D1
D2
D3
D4
D5
D6
D7
WR
RD
IRQ
A0
A1
CS
Doc. # 20480211.002
MODEM