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STV0676

External interfaces

Benchmark testing of the STV0676 indicates that 30fps CIF video (compressed) can be

accommodated in 50% of USB bandwidth.

2.2

Mode selection

All USB devices report a VID, PID and power consumption as part of a standard device descriptor.

The VID and PID for STV0676 can be configured by the state of the digiport bits or by using an

external EEPROM. The mode selection is made using the two MODESEL pins as described in

2.3

Selecting VID and PID via the digiport

Tables 4~7 demonstrate how the VID/PID information is defined via the digiport.

The current reference design for the STV0676-chipset has digiport[7:0] connected to VSS, thus the

VID and PID are 16’h0553 and 16’h0140 respectively.

The digiport also controls the device current consumption that is reported to the host at device

enumeration.

Table 3: Mode selection

MODESEL[1]

MODESEL[0]

Mode of operation

0

0

USB Mode. External EEPROM fitted, therefore PID, VID and power

consumption read from this source. See

Section 2.4

10

0

1

USB mode. Default. No external EEPROM fitted, the PID

VID and power consumption data determined by digiport[7:0].

See

Section 2.3

11

Reserved

Table 4: Basic digiport configuration

digiport bit slice

function

[3:0]

configures the LS nibble of the PID

[5:4]

master VID/PID select

[7:6]

power setting

Table 5: Digiport LS nibble configuration

digiport[3:0]

PID LS nibble

4’b0000

4’b0000

4’b0001

4’b0001

4’b0010

4’b0010

4’b0011

4’b0011

4’b0100

4’b0100

4’b0101

4’b0101