gt3200 SMC Corporation, gt3200 Datasheet - Page 29

• Manufacturer Part Number: gt3200
• Description: Usb2.0 Phy Ic
• Manufacturer: SMC Corporation

USB2.0 PHY IC
SMSC GT3200, SMSC USB3250
DATA[15:8]
RXACTIVE
DATA[7:0]
RXVALID
VALIDH
DP/DM
CLK30
The assertion of RESET will force the Receive State Machine into the Reset state. The Reset state
deasserts RXACTIVE and RXVALID. When the RESET signal is deasserted the Receive State
Machine enters the RX Wait state and starts looking for a SYNC pattern on the USB. When a SYNC
pattern is detected the state machine will enter the Strip SYNC state and assert RXACTIVE. The length
of the received Hi-Speed SYNC pattern varies and can be up to 32 bits long or as short as 12 bits
long when at the end of five hubs. As a result, the state machine may remain in the Strip SYNC state
for several byte times before capturing the first byte of data and entering the RX Data state.
After valid serial data is received, the state machine enters the RX Data state, where the data is loaded
into the RX Holding Register on the rising edge of CLKOUT and RXVALID is asserted. The SIE must
clock the data off the RXDATA bus on the next rising edge of CLKOUT. If OPMODE = Normal, then
stuffed bits are stripped from the data stream. Each time 8 stuffed bits are accumulated the state
machine will enter the RX Data Wait state, negating RXVALID thus skipping a byte time.
When the EOP is detected the state machine will enter the Strip EOP state and negate RXACTIVE
and RXVALID. After the EOP has been stripped the Receive State Machine will reenter the RX Wait
state and begin looking for the next packet.
The behavior of the Receive State Machine is described below:
I
I
I
I
I
I
I
I
Note 7.1
RXACTIVE and RXREADY are sampled on the rising edge of CLKOUT.
In the RX Wait state the receiver is always looking for SYNC.
The USB3280 asserts RXACTIVE when SYNC is detected (Strip SYNC state).
The USB3280 negates RXACTIVE when an EOP is detected and the elasticity buffer is empty
(Strip EOP state).
When RXACTIVE is asserted, RXVALID will be asserted if the RX Holding Register is full.
RXVALID will be negated if the RX Holding Register was not loaded during the previous byte time.
This will occur if 8 stuffed bits have been accumulated.
The SIE must be ready to consume a data byte if RXACTIVE and RXVALID are asserted (RX Data
state).
Figure 7.10
RXACTIVE, RXERROR and RXDATA signals.
Figure 7.9 Receive Timing for 16-bit Data, Odd Byte Count
SYNC
The USB2.0 Transceiver does NOT decode Packet ID's (PIDs). They are passed to the
SIE for decoding.
shows the timing relationship between the received data (DP/DM) , RXVALID,
PID
DATA
0
DATA
1
DATA (0)
DATASHEET
PID
DATA
2
24
DAT
3
A
DATA (1)
DATA (2)
CRC
LO
CRC
HI
CRC (LO)
DATA (3)
EOP
CRC (HI)
Revision 1.3 (10-05-04)