Microcontroller units (or MCUs) can be used in wide variety of applications to control the operation of complex systems. For example, an MCU can be used in an automotive environment to control the operation of vehicle subsystems, such as an inflatable restraint system or a climate control system. When used in such environments, the MCU can be required to monitor the operation of system components by measuring (or sampling) signals used or produced by the components. Often these signals can be analog signals, which are generally defined as signals that are time-varying and continuous.
The analog signals can be sampled and the samples converted to digital values (logical xe2x80x9conesxe2x80x9d and xe2x80x9czeroesxe2x80x9d) using an analog-to-digital (A/D) converter. The A/D converter can be included on an integrated circuit (IC) chip along with the MCU, and the digital values produced by the A/D converter can be used by the MCU to monitor and control the operation of the components. The number of analog signals that can be required to be converted into digital values to monitor and control the operation of a complex system can be great. An MCU IC chip can include a large number of input pins (or terminals) to receive the analog signals.
A single xe2x80x9con-chipxe2x80x9d A/D converter can be used to sample the analog signals presented at several of the input terminals. A control signal, often referred to as a xe2x80x9ctriggerxe2x80x9d, can be used to initiate a conversion. The A/D converter can be configured to operate in a particular manner (or mode) prior to the occurrence of a triggering event. For example, the A/D converter can be configured prior to the occurrence of multiple triggering events to sequentially convert the analog signals presented at several of the input terminals (referred to here as a xe2x80x9csweepxe2x80x9d mode). The A/D converter can also be configured to convert the analog signal presented at only one of the input terminals (referred to here as a xe2x80x9cone-shotxe2x80x9d mode), such that the later occurrence of multiple triggering events can result in the repeated conversion of the analog signal presented at the one input terminal.
With such arrangements, software (or firmware) can be used prior to the occurrence of a triggering event to configure the A/D converter in either the sweep or one-shot mode and to define the corresponding several or one input terminals presenting the analog signal(s) for conversion. U.S. Pat. No. 5,291,197 to Abe describes a one-chip data processor with built-in A/D converter for automatically repeating A/D conversions without instructions from a central processing unit (CPU). U.S. Pat. No. 5,302,952 to Campbell, Jr., et al. describes an A/D conversion module and method to minimize software involvement by providing a pause capacity.
Techniques are disclosed for analog-to-digital signal conversion. According to an exemplary embodiment, a first request is associated with a changeable set of a plurality of input terminals, a second request is associated with a changeable one of the input terminals, and a third request is associated with a fixed one of the input terminals. One of the first, second, and third requests is received, and an analog signal presented at one of the input terminals is converted into a digital value based on the received one of the first, second, and third requests.