CMX878D6 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX878D6' PDF : 63 Pages View PDF
Line Powered Modem plus DAA
CMX878
Definitions of ‘VALID’ and ‘INVALID’: These terms describe the data integrity of the Standby Supply
Registers. The CMX878 monitors the Standby Supply and will set the ‘VALID’ bit (bit 5) of the
Line/Wakeup Event Register accordingly. 1 = ‘VALID’. 0 = ‘INVALID’.
Upon first application of line power (or after a line interruption severe enough to drop SBYVDD below its
acceptable level) this bit will be set to 0 to indicate ‘INVALID’ register contents. When the microcontroller
has read this bit as being ‘INVALID’ it should ignore the value of all other bits read back. It should then
proceed to program both the Configuration Register and the Supplementary Standby Register to the
required values. The Standby Supply Register contents are now ‘VALID’ and bit 5 of the Line/Wakeup
Event Register will be set to 1.
The microcontroller must check the ‘VALID’ status at the start of its program after it has powered up.
Also if the microcontroller is able to detect certain fault conditions (e.g. with a brown-out detector or a
watchdog timer) it should again check the ‘VALID’ status.
All other C-BUS Registers are concerned with the control of functions which operate from the
Regulated Supply, usually with the Line off-hook; for example operation of the MODEM & TONES
PROCESSOR block. Note that these registers will lose their contents whenever the Regulated Supply is
de-powered.
Interrupts: The only register bit which can directly cause an interrupt is bit 14 (IRQ) of the Status
Register and thus all interrupts operate through this bit. When this bit and the IRQNEN bit (bit 6) of the
General Control Register are both 1 then the IRQN output pin will be pulled low (to Vss).
The following C-BUS addresses and registers are used by the CMX878:
Register
Name
General Reset Command
General Control Register
Transmit Mode Register
Receive Mode Register
Transmit Data Register
Receive Data Register
Status Register
Programming Register
Line Control Register
DAC Control Register
ADC Control Register
Configuration Register Write
Configuration Register Read
Supplementary Standby Register Write
Supplementary Standby Register Read
Line/Wakeup Event Register
Type
address only,
no data
16-bit write-only
16-bit write-only
16-bit write-only
8-bit write-only
8-bit read-only
16-bit read-only
16-bit write-only
8-bit write-only
8-bit write-only
8-bit write-only
16-bit write
16-bit read
16-bit write
16-bit read
16-bit read-only
Address
$01
From Supply:
Standby [S] or
Regulated [R]
R
$E0
R
$E1
R
$E2
R
$E3 &
R
$E4
$E5
R
$E6
R
$E8
R
$EC
R
$ED
R
$EE
R
$F0
S
$F1
S
$F2
S
$F3
S
$F4
S
Note: The C-BUS addresses $E9, $EA and $EB are allocated for production testing and should not be
accessed in normal operation.
© 2002 Consumer Microcircuits Limited
27
D/878/2
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