CMX867(2000) View Datasheet(PDF) - CML Microsystems Plc

Part Name

Description

Manufacturer

CMX867
(Rev.:2000)

Low Power V.22 Modem

CML Microsystems Plc 

Low Power V.22 Modem

CMX867

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.

1.5.10 C-BUS Interface

This block provides for the transfer of data and control or status information between the CMX867’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 CMX867’s Write Only Registers, or a one or more byte(s) of data read out from one of the CMX867’s

Read Only Registers, as illustrated in Figure 8.

Data sent from the µC on the Command Data line is clocked into the CMX867 on the rising edge of the Serial

Clock input. Reply Data sent from the CMX867 to the µC is valid when the Serial Clock is high. The CSN 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 14 gives detailed C-BUS timing requirements.

The following C-BUS addresses and registers are used by the CMX867:

General Reset Command (address only, no data).

General Control Register, 16-bit write only.

Transmit Mode Register, 16-bit write-only.

Receive Mode Register, 16-bit write-only.

Transmit Data Register, 8-bit write only.

Receive Data Register, 8-bit read-only.

Status Register, 16-bit read-only.

Programming Register, 16-bit write-only.

Address $01

Address $E0

Address $E1

Address $E2

Addresses $E3 and $E4

Address $E5

Address $E6

Address $E8

Note: The C-BUS addresses $E9, $EA and $EB are allocated for production testing and should not be

accessed in normal operation.

1.5.10.1 General Reset Command

General Reset Command (no data)

C-BUS address $01

This command resets the device and clears all bits of the General Control , Transmit Mode and Receive Mode

Registers and bits 15 and 13-0 of the Status Register.

Whenever power is applied to the CMX867 a General Reset command should be sent to the device, after

which the General Control Register should be set as required.

© 2000 Consumer Microcircuits Limited

17

D/867/1

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