2.1.2 "Reserved" Interfaces
Some of the "Reserved" interfaces are adding extra functionality to an "Always Compatible"
interface. E.g. the additional USB 3.x SuperSpeed signals in the "Reserved" class are required to be
used in conjunction with the USB 2.0 Host interface signals in the "Always Compatible" class. There
are additional RTS/CTS hardware flow control signals which need to be used in conjunction with
the respective general purpose UARTs found in the "Always Compatible" class.
Since "Reserved" interfaces are possibly not provided by some modules, it is mandatory to consult
module datasheets for further information. A useful tool is the Toradex Pinout Designer which
supports comparing the available features of different Verdin modules.
If a module does not feature all possible instances of "Reserved" interfaces (defined by the Verdin
standard), interfaces will be filled in an ascending order (starting from the lowest instance index).
For example, in the Verdin standard, there are two CAN interfaces (CAN_1 and CAN_2). Both are
in the "Reserved" class. If only one CAN is required by a custom carrier board design, it is advisable
to use CAN_1. This guarantees better compatibility with other Verdin modules that e.g. feature a
single CAN interface (CAN_1) only.
Some interfaces (I
2
C and PWM) have instances that are reserved for other interfaces (e.g HDMI).
When filling interfaces during the design of Verdin SoMs, these instances are prioritized according
to the availability of the interface they belong to. For example, there are up to four I
2
C instances in
the Verdin specification (I2C_1, I2C_2_DSI, I2C_3_HDMI, I2C_4_CSI). If a SoC features only three
I
2
C instances and offers no HDMI interface but has a CSI interface, the following interface
interfaces will be provided by the module: I2C_1, I2C_2_DSI and I2C_4_CSI. As the example
shows, in these cases the indices of interfaces provided can be non-continuous.
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