MT8880C
Data Sheet
b3
b2
b1
b0
RSEL
IRQ
CP/DTMF
TOUT
Table 3 - CRA Bit Positions
b3
b2
b1
b0
C/R
S/D
TEST
BURST
Table 4 - CRB Bit Positions
BIT
NAME
FUNCTION
DESCRIPTION
b0
TOUT
TONE OUTPUT
A logic ‘1’ enables the tone output. This function can be
implemented in either the burst mode or non-burst mode.
b1
CP/DTMF
MODE CONTROL
In DTMF mode (logic ‘0’) the device is capable of generating and
receiving Dual Tone Multi-Frequency signals. When the CP (Call
Progress) mode is selected (logic ‘1’) a 6th order bandpass filter is
enabled to allow call progress tones to be detected. Call progress
tones which are within the specified bandwidth
will
be
presented at the IRQ/CP pin in rectangular wave format if
the IRQ bit has been enabled (b2=1). Also, when the CP mode and
BURST mode have both been selected, the transmitter will issue
DTMF signals with a burst and pause of 102 ms (typ) duration. This
signal duration is twice that obtained from the DTMF transmitter if
DTMF mode had been selected. Note that DTMF signals cannot be
decoded when the CP mode of operation has been selected.
b2
b3
IRQ
INTERRUPT ENABLE
REGISTER SELECT
A logic ‘1’ enables the INTERRUPT mode. When this mode is active
and the DTMF mode has been selected (b1=0) the IRQ/CP pin will
pull to a logic ‘0’ condition when either 1) a valid DTMF signal has
been received and has been present for the guard time duration or 2)
the transmitter is ready for more data (BURST mode only).
RSEL
A logic ‘1’ selects Control Register B on the next Write cycle to the
Control Register address. Subsequent Write cycles to the Control
Register are directed back to Control Register A.
Table 5 - Control Register A Description
13
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
