UDA1321 datasheet(18/44 Pages) PHILIPS

18 / 44 page

1998 Oct 06

Philips Semiconductors

Preliminary speciﬁcation

Universal Serial Bus (USB)

Digital-to-Analog Converter (DAC)

UDA1321

Fig.6 Diode matrix selection.

handbook, full pagewidth

MGM109

10 nF

22 pF

USB-B

connector

Vbus

Ω

−

GP5

GP3

GP0

1.5 k

Ω

22 k

Ω

22 k

Ω

22 k

Ω

22 k

Ω

22 k

Ω

22 k

Ω

TR3

TR1

TR2

3.3 V

22 k

Ω

Vbus

KEY 1

SW1

KEY 2

SW2

Start-up and conﬁguration of the UDA1321

START-UP OF THE UDA1321

After power-on, an internal power-on reset signal becomes

HIGH after a certain RC-time (R = 5 k

Ω and C = Cref).

During 10 ms after power-on reset the UDA1321 has to

initiate the internal settings. After the power-on reset the

UDA1321 becomes master of the I2C-bus. The UDA1321

tries to read the eventually connected EEPROM and if an

EEPROM is detected, the internal descriptors are

overwritten and the selected port configuration is applied.

If no EEPROM is detected, the UDA1321 tries to read the

logical levels of GP3 and GP0. A choice can be made from

four configuration maps via these two pins.

CONFIGURATION SELECTION OF THE UDA1321 VIA A DIODE

MATRIX

The UDA1321 uses a configuration map to hold a number

of specific configurable data on hardware, product,

component and USB configuration level. At start-up

without EEPROM, the UDA1321 will scan the logical levels

of GP3 and GP0. With these two pins it is possible to

select one of the four possible (vendor specific)

configuration maps. This selection can be achieved via a

diode matrix (see Fig.6).

After selecting a configuration map the user cannot

change the chosen settings for the GP pins, internal

configuration, descriptors, etc.

For more information about the four (vendor specific)

configuration maps and the diode matrix see the

application documentation.

CONFIGURATION OPTIONS OF THE UDA1321 VIA AN I2C-BUS

EEPROM

If an EEPROM is detected (reading byte 0 as AAH and

byte 1 as 55H), the UDA1321 will use the configuration

map in the EEPROM instead of one of four configuration

maps. The layout of the configuration map is fixed, the

values (except bytes 0 and 1) are user definable (see

Table 6). If the user wants to change these values

(the manufacturers name for instance), this can be

achieved via the EEPROM code.

The communication between the UDA1321 and the

external I2C-bus device is based on the standard I2C-bus

protocol given in the Philips specification

“The I2C-bus and

how to use it (including specifications)”, which can be

ordered using the code 9398 393 40011. The I2C-bus has

two lines: a clock line SCL and a serial data line SDA

(see Fig.7).

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