MT8885
Data Sheet
NOTE: The adaptive micro interface relies on high-to-low transition on CS to recognize the microcontroller
interface. This pin must not be tied permanently low. Only one register access is allowed on any CS assertion.
The adaptive micro interface provides access to five internal registers. The read-only Receive Data Register
contains the decoded output of the last valid DTMF digit received. Data entered into the write-only Transmit Data
Register will determine which tone pair is to be generated (see Table 1 for coding details). Transceiver control is
accomplished with two control registers (see Tables 6 and 7), CRA and CRB, which have the same address. A write
operation to CRB is executed by first setting the most significant bit (b3) in CRA. The following write operation to the
same address will then be directed to CRB, and subsequent write cycles will be directed back to CRA. The read-
only status register indicates the current transceiver state (see Table 8).
A software reset must be included at the beginning of all programs to initialize the control registers upon power-up
or power reset (see Figure 14). Refer to Tables 4-7 for bit descriptions of the two control registers.
The multiplexed IRQ/CP pin can be programmed to generate an interrupt upon validation of DTMF signals or when
the transmitter is ready for more data (burst mode only). Alternatively, this pin can be configured to provide a
square-wave output of the call progress signal. The IRQ/CP pin is an open drain output and requires an external
pull-up resistor (see Figure 13).
Motorola
Intel
RS0
R/W
WR
RD
Function
Write to Transmit
0
0
0
1
1
Data Register
0
1
0
Read from Receive
Data Register
1
1
0
1
0
1
1
0
Write to Control Register
Read from Status Register
Table 3 - Internal Register Functions
b3
b2
b1
b0
RSEL
IRQ
CP/DTMF
TOUT
Table 4 - CRA Bit Positions
b3
b2
b1
b0
C/R
S/D
RxEN
BURST
ENABLE
Table 5 - CRB Bit Positions
13
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
