Use of Mailboxes

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The HSC claims mailbox 1. The DSP send a mailbox value to the host to request some action; the Host eventually sends a mailbox value back as a reply to the DSP. Each 32-bit value is interpreted as follows:

typedef struct {

unsigned int Data : 25; // data value

unsigned int Fn : 4; // function code

unsigned int Channel : 3; // channel selector

} HSC_WORD;

#define HscChannel(v) (*(HSC_WORD *)&(v)).Channel

#define HscFn(v) (*(HSC_WORD *)&(v)).Fn

#define HscData(v) (*(HSC_WORD *)&(v)).Data

	Channel	selects one of the eight available high-speed channels.
	Fn	holds a function code that the DSP uses to inform the host what is to be done. The host may set Fn to the values 0 (OK) or 1 (Error) only.
	Data	holds a parameter value for the selected function.