MDI

The idea

Your friendly neigbourhood message based shared memory communication protocol; used between the MCU and DSP (in MAD).

There are two message types: short and long. Short is one halfword, long packets use a FIFO queue and can be quite somewhat longer.

This is used to transfer FBUS and GSM packets to the approciate interface, and for a lot of other parameters as well. In this section the various MDI types and their packet contents will be analysed.

Long MDI is coordinated through two queues in the Shared Memory range, MDISND and MDIRCV. The two queues have an head and a tail which tell how many bytes are in it and where to write or read. It always does in halfword quantities (because that's how the DSP works).

• MCU must process the MDI RCV queue on FIQ0.
• DSP will process the MDI SND queue on DSP interrupt (make sure you don't generate an interrupt on every packet when sending back-to-back and the queue is not full yet, interrupts slow down processing..)

Short MDI packets are seperate halfword, they are put in the approciate place in shared memory and an interrupt is generated:

• MCU->DSP: Places command in "MCU->DSP short MDI command" and invokes DSP interrupt.
• DSP->MCU: Places command in "DSP->MCU short MDI command" and invokes IRQ4 interrupt.

The format

... todo ...

Last updated: 2005-02-21 14:19

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