SPRADO3B December 2024 – September 2025 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
For the MCSPI interface, the recommendation is to provide series resistors (22Ω) for SPI clock output signals SPI0..2_CLK (MCSPI 0..2) and MCU_SPI0..1_CLK (MCU_MCSPI 0..1) close to processors clock output pin (processor MCSPI is configured as controller) since the clock output is used for retiming.
For the MCASP interface, the recommendation is to provide series resistors (22Ω) for transmit clock (Transmit Bit Clock) output signals MCASP0..2_ACLKX and Transmit Frame Sync signals MCASP0..2_AFSX close to processors clock output pin (processor MCASP is configured to source the clock) since the clock output is used for retiming.
The recommendation is to add a pulldown (10kΩ) (close to attached device clock input pin) to hold the attached device in low state (there are cases where the clock is stopped or paused in a low logic state and the pulldown option is consistent with this logic state) for all IOs configured for MCSPI and MCASP interfaces.
The recommendation is to provide series resistors (22Ω) for receiver clock (Receive Bit Clock) output signals MCASP0..2_ACLKR and Receive Frame Sync signals MCASP0..2_AFSR (close to attached device).
For a number of processor IOs (LVCMOS or SDIO), the IO buffers TX (Output) and RX (Input) are disabled and internal pulls (pullup and pulldown) are turned off during reset and after reset. The recommendation is to verify if external pullups (10kΩ or 47kΩ) are provided for SPI Chip Select SPI0..2_CS0..3 (MCSPI 0..2) and MCU_SPI0..1_CS0..3 (MCU MCSPI 0..1) (close to attached device). The recommendation is to add pulls (10kΩ or 47kΩ) to the processor and the attached device signals (data interface - data in, data out) that can float (to prevent the attached device inputs from floating until driven by the host).
Two (x2) or more devices (common clock connection, different data signals connection, working simultaneously) are allowed to be connected to MCASP interface. The MCASP can be configured to have the transmit and receive sections operate synchronously to the transmit section clock and transmit frame sync signals. The BCLK and frame sync need to be the same for all target devices if using dedicated serializers, not an issue if using TDM. During custom board design, the potential of signal quality/signal reflections (signal reflections caused by driving multiple inputs from a single MCASP clock output) is something to be considered.