AN2282

Firmware

11/19

typedef struct{

unsigned char buff[1600];

unsigned short dim;

unsigned type;

} mblk_t;

The messages to be transmitted are managed by two linked lists of requests inside a static

array of transmission requests. It is possible to manage up to 16 outstanding requests. The

request structure is as follows:

struct txreq

{

struct txreq

*pNext;

PIA

pDestAddr;

mblk_t

*pMsg;

unsigned short Length;

unsigned short Type;

};

typedef struct txreq TXREQ, *PTXREQ;

The first list is composed of the outstanding transmission requests, the second one of the

unused requests. The functions for message management are:

●

unsigned long csSend( PIA pDestAddr, mblk_t *pSendParms );

This routine is called when a new message has to be transmitted. The Destination

address and the message are passed by the arguments. The new transmit request is

placed on the transmit request queue. If a transmit request is not currently in progress

then the new transmit request is started, else it waits its turn in queue.

●

unsigned short csRequestTransmit(void);

This routine requests that a transmit be started by writing a transmit command and a

frame length to the chip. The content of the BusStatus register is returned which

indicates the success of the request.

●

void csCopyTxFrame(void);

This routine builds an Ethernet header in the chip's transmit frame buffer and then

copies the frame data from the list of message blocks to the chip's transmit frame

buffer. When all the data has been copied then the chip automatically starts to transmit

the frame.

●

void csProcessISQ(void);

This routine processes the events on the Interrupt Status Queue. The events are read

one at a time from the ISQ and the appropriate event handlers are called. The ISQ is

read until it is empty. If the chip's interrupt request line is active, then reading a zero

from the ISQ will deactivate the interrupt request line.

●

void csReceiveEvent( unsigned short RxEvent );

This routine is called whenever a frame has been received at the chip. This routine

copies the received frame into the data buffer of the reception message and passes the

message to the upper layer by calling Announce_Packet() entry point of the upper

layer. Moreover, this routine verifies that the frame type is acceptable.

●

void csTransmitEvent(void);

This routine is called whenever the transmission of a frame has completed (either

successfully or unsuccessfully). This routine removes the completed transmit request