SNAS835A September 2022 – February 2025 LMK5B33414
PRODUCTION DATA
When SPI control interface is selected, the device uses a 3-wire SPI with SDIO, SCK, and SCS signals (SPI_3WIRE_DIS = 0). When using SPI SCS_ADD also can act as a Time Elapsed Counter (TEC) trigger. When set SPI_3WIRE_DIS = 1, any GPIO can be selected as SDO to support readback with 4-wire SPI.
The host device must present data to the device MSB first. A message includes a transfer direction bit ( W/R), a 15-bit address field (A14 to A0), and a 8-bit data field (D7 to D0) as shown in Figure 8-44. The W/R bit is 0 for a SPI write and 1 for a SPI read.
A message frame is initiated by asserting SCS low. The frame ends when SCS is deasserted high. The first bit transferred is the W/R bit. The next 15 bits are the register address, and the remaining eight bits are data. On write transfers, data is committed in bytes as the final data bit (D0) is clocked in on the rising edge of SCK. If the write access is not an even multiple of eight clocks, the trailing data bits are not committed. On read transfers, data bits are clocked out from the SDO pin on the falling edges of SCK.
The LMK5B33414 supports a SPI block write and block read transfers. A SPI block transfer is exactly (2 + N) bytes long, where N is the number of data bytes to write or read. The host device (SPI host) is only required to specify the lowest address of the sequence of addresses to be accessed. The device automatically increments the internal register address pointer if the SCS pin remains low after the host finishes the initial 24-bit transmission sequence. Each transfer of eight bits (a data payload width) results in the device automatically incrementing the address pointer (provided the SCS pin remains active low for all sequences).