The aperiodic mode of the A629 module allows an application to transmit without using a major frame. This mode should not be confused with the aperiodic mode of a frame (when the time it takes to transmit the data is longer than the TI).

The KMXF_A629_MODULE_APERIODIC_MODE attribute holds the module Tx Aperiodic Mode enable state. When enabled, the transmission is not based on the A629 timers (TI, SG and TG) but controlled by the application.

There are limitations to keep in mind when using this mode.

Only the first RT channel of a module can be used.
No major frame can be used.
The RT channel should be the only transmitter on the bus, otherwise collision could happen since no A629 timers are used.
The A629 module FIFO depth is fixed at 512 words. This means that the firmware will always try to keep the module FIFO full and the aperiodic buffer message count only reports the number of records in the aperiodic buffer of the firmware side. If MXF_ASYNCEVENT_COND_TXAPERIODIC_BUFFER_THRESHOLD asynchronous event condition is used, it will be affected the same way.

mxfTxAperiodicWrite() function is used for transmission with MXF_A629_DATAREC structure for data. The first wordstring of a message should have the MXF_A629_TX_REC_CTRL_PPSYNC and MXF_A629_TX_REC_CTRL_PSYNC bit sets in the control field. MXF_A629_TX_REC_CTRL_CRC control bit must be set if a CRC must be appended after the last word. Label (bit 0..11) and CID (bit 12..15) must be set in data[0].

This mode should be used only for special test cases.

Example

ar629_aperiodic_mode.c