The 12 pins of AIO_MUX2 can be selectively mapped through a dedicated set of registers to 12 analog inputs for ADC2 peripheral, six analog inputs for Comparator peripherals, four General-Purpose Inputs, or four General-Purpose Outputs. While AIO_MUX2 has been named after the analog signals passing through it, the GPIOs (here called AIOs) are still digital, although with fewer features than those in the GPIO_MUX1 and GPIO_MUX2 blocks—for example, they do not offer pullups. On reset, all pins of the AIO_MUX2 block are configured as analog inputs and the GPIO function is disabled. The AIO_MUX2 block is programmed through a separate set of registers from those used to program AIO_MUX1.
The multiple registers responsible for configuring the AIO_MUX2 pins are accessible by the C28x CPU only. The bottom portion of Figure 6-17 shows Control Subsystem registers and muxing logic for the associated 12 AIO pins. The AIOMUX2 register selects 1 of 12 possible analog input signals or 1 of 6 general-purpose AIO inputs. Other registers allow reading and writing of the 6 AIO bits, as well as setting the direction for each of the bits (read or write). See Table 6-32 for the mapping of analog inputs and AIOs to the 12 pins of AIO_MUX2. Peripheral Modes 1 and 2 are currently not available.
AIO Mode 0 is chosen by setting selected odd bits of the AIOMUX2 register to ‘0’. AIO Mode 1 is chosen by setting selected odd bits of the AIOMUX2 register to ‘1’. For example, setting bit 9 of the AIOMUX2 register to ‘0’ assigns pin ADC2INA4 to internal signal AIO20 (digital GPIO). Setting bit 9 of the AIOMUX2 register to ‘1’ assigns pin ADC2INA4 to analog inputs ADC2INA4 or COMPA5 (only one should be enabled at a time in the respective analog module). Currently, all even bits of the AIOMUX2 register are “don’t cares”.
|DEVICE PIN NAME||C28x AIO MODE 0(3)||C28x AIO MODE 1(4)|