SWRU455M February 2017 – October 2020 CC3120 , CC3120MOD , CC3130 , CC3135 , CC3135MOD , CC3220MOD , CC3220MODA , CC3220R , CC3220S , CC3220SF , CC3230S , CC3230SF , CC3235MODAS , CC3235MODASF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
During initialization, the nHIB pin is asserted (to enable the device), while the nRESET pin is kept high. At this stage, the HOST_IRQ pin should be driven low by the device until initialization is complete. During this time, and until HOST_IRQ is asserted for the first time, the host must not communicate with the device, otherwise the communication with the device might not be established.
After the Host IRQ has been asserted for the first time, the host writes a sync word to the device. This causes the host interrupt to prepare the message to the host and clear the IRQ line. The process is described in Figure 25-6.
When the sync word has been written by the host, the device knows the host will now read the message that caused the IRQ to rise (in this case, initialization complete).
Because the host may precede the device’s data readiness, there is another synchronization word that the host is looking for before parsing the response. All data before the data ready synchronization word is discarded by the driver. In some or even most cases, the first word read from the device is the synchronization word, and no superfluous reads are made.
If the host sends a sync word for read while there is no message to send from the SimpleLink device to the host, the SimpleLink device sends a dummy message to avoid synchronization loss.