MT8880C/MT8880C-1
BIT
b0
NAME
BURST
FUNCTION
BURST MODE
ISO
2
-CMOS
DESCRIPTION
A logic ‘0’ enables the burst mode. When this mode is
selected, data corresponding to the desired DTMF tone pair
can be written to the Transmit Register resulting in a tone
burst of a specific duration (see AC Characteristics).
Subsequently, a pause of the same duration is induced.
Immediately following the pause, the Status Register is
updated indicating that the Transmit Register is ready for
further instructions and an interrupt will be generated if the
interrupt mode has been enabled. Additionally, if call
progress (CP) mode has been enabled, the burst and pause
duration is increased by a factor of two. When the burst
mode is not selected (logic ‘1’) tone bursts of any desired
duration may be generated.
By enabling the test mode (logic’1’), the IRQ/CP pin will
present the delayed steering (inverted) signal from the DTMF
receiver. Refer to Figure 9 (b3 waveform) for details
concerning the output waveform. DTMF mode must be
selected (CRA b1=0) before test mode can be implemented.
A logic ‘0’ will allow Dual Tone Multi-Frequency signals to be
produced. If single tone generation is enabled (logic ‘1’),
either row or column tones (low group or high group) can be
generated depending on the state of b3 in Control Register
B.
When used in conjunction with b2 (above) the transmitter
can be made to generate single row or single column
frequencies. A logic ‘0’ will select row frequencies and a logic
‘1’ will select column frequencies.
b1
TEST
TEST MODE
b2
S/D
SINGLE /DUAL TONE
GENERATION
b3
C/R
COLUMN/ROW TONES
Table 6
.
Control Register B Description
BIT
b0
b1
NAME
IRQ
TRANSMIT DATA
REGISTER EMPTY
(BURST MODE ONLY)
RECEIVE DATA
REGISTER FULL
DELAYED STEERING
STATUS FLAG SET
Interrupt has occurred. Bit one (b1)
or bit two (b2) is set.
Pause duration has terminated
and transmitter is ready for new
data.
Valid data is in the Receive Data
Register.
Set upon the valid detection of the
absence of a DTMF signal.
STATUS FLAG CLEARED
Interrupt is inactive. Cleared after
Status Register is read.
Cleared after Status Register is
read or when in non-burst mode.
Cleared after Status Register is
read.
Cleared upon the detection of a
valid DTMF signal.
b2
b3
Table 7. Status Register Description
4-42
MITEL [ MITEL NETWORKS CORPORATION ]
