DTMF Generator Code for MT8888 Interface with 80C51

Thread Starter


Joined Dec 29, 2006

I am trying to develop PC based Dialler using MT8888 Transreceiver interfaced with 80C51.

Can you give source code in C how to interface the MT8888.

Specially I donot know how select the Control Register CRA & CRB bits

If there any example code in c please suggest me

Prev Ravanth


Joined Feb 24, 2006
CRA and CRB are both at the same address. You need to read the datasheet carefully. Here is the appropriate excerpt
Rich (BB code):
The microprocessor 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).