SLLA640 April   2025 ISO1228

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1ISO1228 - Relevant Device Information
  5. 2Parallel and Serial Output Modes
  6. 3Switching Communication Modes During Operation
    1. 3.1 Parallel to Serial
    2. 3.2 Serial to Parallel
  7. 4SPI Functional Modes
    1. 4.1 Normal Mode
      1. 4.1.1 Normal Mode - Read IN8-IN1 Continuously
    2. 4.2 Burst Mode
  8. 5Maximum Data Throughput in Serial Mode
  9. 6Digital Low Pass Filtering of Outputs
  10. 7Summary
  11. 8References

3.1 Parallel to Serial

A parallel to serial mode transition needs to be executed as shown in the following when starting in parallel mode (COMM_SEL = 0):

  1. Make sure that all MCU pins connected to the output pins of the ISO1228 (pins 35 to 28) are tristated.
  2. Switch COMM_SEL = 1 to transition from parallel to serial mode. The ISO1228 can also tristate the OUTx pins needed for SPI (pins 35 to 32) until the mode switch is complete.
  3. Wait for a minimum of 30ns to allow IO buffers to change from output mode to serial mode glitch-free
  4. Drive nRST=0 (pin 30) for a minimum of 35ns to allow a full reset of the SPI logic inside ISO1228
  5. Release nRST = 1 and wait for a minimum of 200ns
  6. ISO1228 is now in serial mode.
  7. Start a SPI transaction by pulling nCS = 0 (pin 32)

ISO1228 can be switched from parallel to serial mode in less than 300ns. The state of OUTx pins in this window needs to be ignored. Figure 3-1 shows the typical timing waveform for the previous steps.

Parallel to Serial Transition Timing Figure 3-1 Parallel to Serial Transition Timing