Variable Clock Rate I2C Bus Adapter FAQ

What is the Variable Clock Rate I2C Bsu Adapter (#MIIC-201-V)?

The Variable Clock Rate I2C Bus Host Adapter (#MIIC-201-V) was specifically developed for semiconductor companies that need to test new ICs that are not completely functional, and cannot operate the I2C bus at normal clock rates. This I2C Bus adapter can master the bus at very slow clock rates.

The Variable Clock Rate Host Adapter is based on our iPort technology and DLL interface, but with two important changes. First, the Variable Clock Rate adapter includes additional hardware that permits the variable control of the master clock rate. The rates supported are 451 Hz to 57 KHz, with a 256 step resolution. Second, the Variable Clock Rate adapter interprets the normal iPort BusTimeOut parameter as its Master Clock Rate parameter.

The iPort Utility Pack Software (Message Center and Message Manager) included with the Variable Clock Host Adapter has been altered to allow a user to set the master clock rate. A user writing a custom program can also set the master clock rate by setting the value of the BusTimeOut parameter in the I2COpen() function call. The following is the Pascal code we use in our software to set the BusTimeOut parameter based upon a user input clock rate of 451 Hz to 57 KHz:

if ((dp.BusTimeOut < 451) or (dp.BusTimeOut > 57000)) then // Clock Rate Range Check
   begin
   MessageDlg('I2C Bus Master Bit Rate OUT-OF-RANGE', mtInformation,[mbOK], 0);
   Exit;
   end;

dp.BusTimeOut := 256-(115000 div (dp.BusTimeOut)); // Set Clock Rate

Inside the Variable Clock adapter, the BusTimeOut value is loaded into an 8-bit timer use the control the bus speed.

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