DP83932C datasheet(23/98 Pages) NSC

23 / 98 page

40 SONIC Registers (Continued)

TLF10492 – 21

FIGURE 4-1 CAM Organization

SONIC is in software reset The CDA resides in the same

64k byte block of memory as the Receive Resource Area

(RRA) and contains descriptors for loading the CAM regis-

ters These descriptors are contiguous and each descriptor

consists of four 16-bit fields

(Figure 4-2) In 32-bit mode the

upper word Dk3116l is not used The first field contains

the value to be loaded into the CAM Entry Pointer and the

remaining fields are for the three CAM Address Ports (see

Section 4310) In addition there is one more field after the

last descriptor containing the mask for the CAM Enable reg-

ister Each of the CAM descriptors are addressed by the

CAM Descriptor Pointer (CDP) register

After the system has initialized the CDA it can issue the

Load CAM command to program the SONIC to read the

CDA and load the CAM The procedure for issuing the Load

CAM command is as follows

1 Initialize the Upper Receive Resource Address (URRA)

within the same 64k Page as the Receive Resource

Area (See Section 439)

2 Initialize the CDA as described above

3 Initialize the CAM Descriptor Count with the number of

CAM descriptors Note only the lower 5 bits are used in

this register The other bits are don’t cares (See Section

4310)

4 Initialize the CAM Descriptor Pointer to locate the first

descriptor in the CDA This register must be reloaded

each time a new Load CAM command is issued

5 Issue the Load CAM command (LCAM) in the Command

If a transmission or reception is in progress the CAM DMA

function will not occur until these operations are complete

When the SONIC completes the Load CAM command the

CDP register points to the next location after the CAM en-

able field and the CDC equals zero The SONIC resets the

LCAM bit in the Command register and sets the Load CAM

Done (LCD) bit in the ISR

TLF10492 – 22

FIGURE 4-2 CAM Descriptor Area Format

DP83932C Datasheet(PDF) 23 Page - National Semiconductor (TI)