ST & T UPSD3212C - Manual (Page 76)

uPSD3212A, uPSD3212C, uPSD3212CV
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USB HARDWARE
The characteristics of USB hardware are as fol-
lows:
■ Complies with the Universal Serial Bus
specification Rev. 1.1
■ Integrated SIE (Serial Interface Engine), FIFO
memory and transceiver
■ Low speed (1.5Mbit/s) device capability
■ Supports control endpoint0 and interrupt
endpoint1 and 2
■ USB clock input must be 6MHz (requires MCU
clock frequency to be 12, 24, or 36MHz).
The analog front-end is an on-chip generic USB
transceiver. It is designed to allow voltage levels
equal to V
DD
from the standard logic to interface
with the physical layer of the Universal Serial Bus.
It is capable of receiving and transmitting serial
data at low speed (1.5Mb/s).
The SIE is the digital-front-end of the USB block.
This module recovers the 1.5MHz clock, detects
the USB sync word and handles all low-level USB
protocols and error checking. The bit-clock recov-
ery circuit recovers the clock from the incoming
USB data stream and is able to track jitter and fre-
quency drift according to the USB specification.
The SIE also translates the electrical USB signals
into bytes or signals. Depending upon the device
USB address and the USB endpoint.
Address, the USB data is directed to the correct
endpoint on SIE interface. The data transfer of this
H/W could be of type control or interrupt.
The device’s USB address and the enabling of the
endpoints are programmable in the SIE configura-
tion header.
USB related registers
The USB block is controlled via seven registers in
the memory: (UADR, UCON0, UCON1, UCON2,
UISTA, UIEN, and USTA).
Three memory locations on chip which communi-
cate the USB block are:
■ USB endpoint0 data transmit register (UDT0)
■ USB endpoint0 data receive register (UDR0)
■ USB endpoint1 data transmit register (UDT1)
Table 60. USB Address Register (UADR: 0EEh)
Table 61. Description of the UADR Bits
7 6 5 4 3 2 1 0
USBEN UADD6 UADD5 UADD4 UADD3 UADD2 UADD1 UADD0
Bit Symbol R/W Function
7 USBEN R/W
USB Function Enable Bit.
When USBEN is clear, the USB module will not respond to any tokens
from host.
RESET clears this bit.
6 to 0
UADD6 to
UADD0
R/W
Specify the USB address of the device.
RESET clears these bits.