MT8888C
Data Sheet
BIT
NAME
DESCRIPTION
b0
BURST
Burst Mode Select. A logic high deactivates burst mode; a logic low enables burst mode.
When activated, the digital code representing a DTMF signal (see Table 1) can be written
to the transmit register, which will result in a transmit DTMF tone burst and pause of equal
durations (typically 51 msec). Following the pause, the status register will be updated (b1 -
Transmit Data Register Empty), and an interrupt will occur if the interrupt mode has been
enabled.
When CP mode (control register A, b1) is enabled the normal tone burst and pause
durations are extended from a typical duration of 51 msec to 102 msec.
When BURST is high (deactivated) the transmit tone burst duration is determined by the
TOUT bit (control register A, b0).
b1
b2
b3
TEST
S/D
Test Mode Control. A logic high enables the test mode; a logic low deactivates the test
mode. When TEST is enabled and DTMF mode is selected (control register A, b1=0), the
signal present on the IRQ/CP pin will be analogous to the state of the DELAYED
STEERING bit of the status register (see Figure 7, signal b3).
Single or Dual Tone Generation. A logic high selects the single tone output; a logic low
selects the dual tone (DTMF) output. The single tone generation function requires further
selection of either the row or column tones (low or high group) through the C/R bit (control
register B, b3).
C/R
Column or Row Tone Select. A logic high selects a column tone output; a logic low selects
a row tone output. This function is used in conjunction with the S/D bit (control register B,
b2).
Table 7 - Control Register B Description
BIT
NAME
STATUS FLAG SET
STATUS FLAG CLEARED
b0
IRQ
Interrupt has occurred. Bit one
(b1) or bit two (b2) is set.
Interrupt is inactive. Cleared after
Status Register is read.
b1
TRANSMIT DATA
REGISTER EMPTY
(BURST MODE ONLY)
Pause duration has terminated
and transmitter is ready for new
data.
Cleared after Status Register is
read or when in non-burst mode.
b2
b3
RECEIVE DATA REGISTER
FULL
Valid data is in the Receive Data
Register.
Cleared after Status Register is
read.
Set upon the valid detection of
the absence of a DTMF signal.
Cleared upon the detection of a
valid DTMF signal.
DELAYED STEERING
Table 8 - Status Register Description
14
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
