microsystems on silicon

DOCITM Interface

The DOCITM interface is a single wire interface between a MOS device and any micro controller. DOCITM is an acronym for Data Out Clock In.

doci schematic image

Serial data transfer between the device and the micro-controller is done exclusively on the DOCITM pin. The DOCITM pin combines functions of a clock input as well as a current limited output driver. The MOS device indicates a successful sample by pulling the DOCITM pin to VDD. To read a data bit, the micro-controller generates a zero to one transition and releases DOCITM line. Depending on the data bit value, the MOS device will keep the DOCITM pin high or pull it low through its output driver. The settling time depends on the total capacitive load on the DOCI pin, typically 1 micro second. The micro-controller samples the value and generates (drives) a new zero to one transition. This process is repeated until all the data bits is clocked out. The first bit read is the most significant bit. After the last bit has been read, the micro-controller must set DOCITM to zero and release it to enable the MOS device to flag that the next sample is ready to be clocked out.

If the reading process is interrupted for longer than tREP and DOCITM is at zero, the serial data register will be updated with a new sample.

The DOCITM pin can be used as an interrupt to the micro-controller indicating that data is ready to be clocked out of the device.

There are small variations on the protocol for various devices and detectors. More specific information regarding reading data form the devices as well as reading data simultaneously from multiple devices can be found in the following documents: