2.1.26 Analog System Builder with ACM Access

This use model is applicable when access to the Analog Configuration multiplexer (ACM) is required during normal system operation. A primary use case is accessing the Real Time Counter (RTC) registers for calendar or real‑time applications. Alternatively, the ACM can be used to access analog I/O configuration registers.

In this configuration, the Analog System Builder (ASB) exposes additional ports that allow access to the ACM. For more information, see ASB Advanced Options – ACM Bus section.

The ACM interface must operate at a frequency below 10 MHz, and user logic that directly interfaces with the ACM must run at the same clock frequency as SLOWCLK.

As an alternative, synchronization logic can be inserted between user logic and the ACM interface. This approach allows user logic to operate at a clock frequency independent of the ACM clock. Figure 17 shows the configuration used when the ACM bus is accessed as part of the INIT/CFG interface.

If the ACM Bus Independent option is selected in the ASB Advanced Options, the multiplexer shown in the following figure is instantiated within the Analog System Builder, and user logic connects directly to the ACM bus interface.