UAC 3552A
PRELIMINARY DATA SHEET
2.1.7. Special I/O
2.2. Software
2.1.7.1. SOF (Start of Frame)
The functionality of the UAC 3552A is mainly defined
by software. The internal µ-controller handles the USB
requests whereas the Audio Processing Unit pro-
cesses the sound features.
The SOF-pin provides a 1-ms signal which is synchro-
nous to the USB 1-ms frame rate. It can be used for
test purpose or as an USB-synchronous reference for
vendor-specific external circuitry.
2.2.1. USB Microcontroller Software
2.2.1.1. Chapter 9 Functions
2.1.7.2. AUXEN
This is a digital input that has to be used if an analog
signal is connected to the AUX R/L pins. It triggers the
microcontroller to switch the input mixer to the analog
input (the DAC signal always remains active!) and it
keeps the device from entering the low-power mode
which can be requested by the host PC or by discon-
necting the device from the USB.
The chapter 9 of the USB Spec 1.1 defines the USB
device framework which is the middle layer of the USB
protocol hierarchy (see USB Spec 1.1 page 175). It
handles routing data between the bus interface and
various endpoints. The endpoint is a source or sink for
data within the device.
2.2.1.2. Device Descriptor
2.1.7.3. SUSPEND
Unlike the configuration descriptor, which is located in
ROM, the device descriptor is more flexible. The man-
ufacturer-related data are stored in the on-chip
EEPROM, and can be adapted individually. In detail
these data are
The SUSPEND pin indicates the low-power mode. It
can be used to power down external circuitry, like
power amplifiers in an USB speaker.
– vendor ID
Table 2–3: SUSPEND pin
– product ID
SUSPEND
– device release number
– manufacturer string
– product string
low
normal power
low power
high
– serial number string
A comfortable programming tool allows this data to be
defined and writes it into the corresponding EEPROM
location.
2.1.8. Clock System
The UAC 3552A is shipped with the Micronas device
descriptor and allows USB functionality without any
EEPROM reprogramming.
The UAC 3552A requires a 12-MHz clock source,
which is realized as an on-chip oscillator with external
crystal. Also an external oscillator can be used. In this
case, the clock has to be connected to XTI. The
12 MHz is the input clock for a PLL circuit which gener-
ates all clocks needed within the IC.
2.2.1.3. String Descriptor
The string descriptor is located in the EEPROM. The
UAC 3552A holds three strings. The programming tool
handles the programming of strings and will take care
of string length control also.
The UAC 3552A is shipped with the Micronas string
descriptor and allows USB functionality without any
EEPROM reprogramming.
10
Micronas
MICRONAS [ MICRONAS ]
