ISO2-CMOS MT8880C/MT8880C-1
RS0
R/W
FUNCTION
b3
b2
b1
b0
0
0
Write to Transmit
Data Register
RSEL
IRQ
CP/DTMF
TOUT
Table 3. CRA Bit Positions
0
1
1
1
0
1
Read from Receive
Data Register
Write to Control
Register
b3
b2
b1
b0
Read from Status
Register
C/R
S/D
TEST
BURST
Table 2. Internal Register Functions
Table 4. CRB Bit Positions
BIT
NAME
FUNCTION
DESCRIPTION
b0
b1
TOUT
TONE OUTPUT
A logic ‘1’ enables the tone output. This function can be
implemented in either the burst mode or non-burst mode.
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
4-41
MITEL [ MITEL NETWORKS CORPORATION ]
