CMX868E2 View Datasheet(PDF) - MX-COM Inc
Part Name
Description
MFG CO.
'CMX868E2' PDF : 43 Pages View PDF
Low Power V.22bis Modem
16
CMX868 Advance Information
In order that received Break signals can be handled correctly in V.14 Rx over-speed mode, a received
character which has all bits ‘0’, including the Stop and any Parity bits, will always cause the Rx Framing Error
bit to be set and the USART to re-synchronize onto the next ‘1’ – ‘0’ transition. Additionally the received
Continuous 0s detector will respond when more than 2M + 3 consecutive ‘0’s are received, where ‘M’ is the
selected total number of bits per character including Stop and any Parity bits.
4.10 C-BUS Interface
This block provides for the transfer of data and control or status information between the CMX868’s internal
registers and the µC over the C-BUS serial bus. Each transaction consists of a single Register Address byte
sent from the µC which may be followed by a one or more data byte(s) sent from the µC to be written into one
of the CMX868’s Write Only Registers, or a one or more byte(s) of data read out from one of the CMX868’s
Read Only Registers, as illustrated in Figure 16.
Data sent from the µC on the Command Data line is clocked into the CMX868 on the rising edge of the Serial
Clock input. Reply Data sent from the CMX868 to the µC is valid when the Serial Clock is high. The CS line
must be held low during a data transfer and kept high between transfers. The C-BUS interface is compatible
with most common µC serial interfaces and may also be easily implemented with general-purpose µC I/O pins
controlled by a simple software routine. Figure 24 gives detailed C-BUS timing requirements.
The following C-BUS addresses and registers are used by the CMX868:
x General Reset Command (address only, no data). Address $01
x General Control Register, 16-bit write-only.
Address $E0
x Transmit Mode Register, 16-bit write-only.
Address $E1
x Receive Mode Register, 16-bit write-only.
Address $E2
x Transmit Data Register, 8-bit write-only.
Addresses $E3 and $E4
x Receive Data Register, 8-bit read-only.
Address $E5
x Status Register, 16-bit read-only.
Address $E6
x Programming Register, 16-bit write-only.
Address $E8
Note: The C-BUS addresses $E9, $EA and $EB are allocated for production testing and should not be
accessed in normal operation.
¤2001 MX-COM, Inc.
www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054
Doc. # 20480205.007
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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