9.1.2 GPIO Ports for Communication

Most microcontrollers have programmable input/output (I/O) pins that can be set in software to act as inputs or outputs. If an SPI controller is not available, the ADS1018 can be connected to GPIO pins and the SPI bus protocol can be simulated. Using GPIO pins to generate the SPI interface requires only that the pins be configured as push or pull inputs or outputs. Furthermore, if the SCLK line is held low for more than 28 ms, communication times out. This condition means that the GPIO ports must be capable of providing SCLK pulses with no more than 28 ms between pulses.