Datasheet

00
0010
XX
(a)
(b) (c)
FF (data-on)D0–D7
CTL0, CTL1
PCLK
TSB81BA3E
SLLS783A –MAY 2009–REVISED MAY 2010 www.ti.com
Figure 26. Null Packet Reception Timing
The sequence of events for a null packet reception is as follows:
a. Receive operation initiated. The PHY indicates a receive operation by asserting receive on the CTL lines.
Normally, the interface is idle when receive is asserted. However, the receive operation can interrupt a status
transfer operation that is in progress so that the CTL lines can change from status to receive without an
intervening idle.
b. Data-on indication. The PHY asserts the data-on indication code on the D lines for one or more cycles.
c. Receive operation terminated. The PHY terminates the receive operation by asserting idle on the CTL lines.
The PHY asserts at least one idle cycle following a receive operation.
Table 35. Receive Speed Codes and Format
D0-D7
(1)
DATA RATE AND FORMAT
0000 0000 S100 legacy
0000 0001 S100 Beta
0000 0100 S200 legacy
0000 0101 S200 Beta
0000 1000 S400 legacy
0000 1001 S400 Beta
0000 1101 S800 Beta
1111 1111 Data-on indication
All others Reserved
(1) Y = Output as 1 by PHY, ignored by LLC.
X = Output as 0 by PHY, ignored by LLC
Transmit
When the LLC issues a bus request through the LREQ terminal, the PHY arbitrates to gain control of the bus. If
the PHY wins arbitration for the serial bus, then the PHY-LLC interface bus is granted to the LLC by asserting
the grant state (11b) on the CTL terminals and the grant type on the D terminals for one PCLK cycle, followed by
idle for one clock cycle. The LLC then takes control of the bus by asserting either idle (00b), hold (11b), or
transmit (01b) on the CTL terminals. If the PHY does not detect a hold or transmit state within eight PCLK cycles,
then the PHY takes control of the PHY-link interface. The hold state is used by the LLC to retain control of the
bus while it prepares data for transmission. The LLC can assert hold for zero or more clock cycles (that is, the
LLC need not assert hold before transmit). During the hold state, the LLC is expected to drive the D lines to 0.
The PHY asserts data-prefix on the serial bus during this time.
When the LLC is ready to send data, the LLC asserts transmit on the CTL terminals as well as sending the first
bits of packet data on the D lines. The transmit state is held on the CTL terminals until the last bits of data have
been sent. The LLC then asserts either hold or idle on the CTL terminals for one clock cycle. If the hold is
asserted, then the hold is immediately followed by one clock cycle of idle. The link then releases the PHY-link
interface by putting the CTL and D terminals in a high-impedance state. The PHY then regains control of the
PHY-link interface.
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