LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
Datasheet
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
137
4.7.6
Source Synchronous-Serial Media Independent Interface
Some system designs require the PHY to be placed between 3 to 12 inches away from the MAC. A
new Source Synchronous-Serial Media Independent Interface (SS-SMII) definition has been added
because of this requirement. To provide a source synchronous interface between the PHY and
MAC, the PHY must drive the RxCLK and the RxSYNC signals to the MAC. Also, the MAC must
drive the TxCLK and the TxSYNC signal to the PHY. The REFCLK is also needed to synchronize
the data to the PHY’s core clock domain. TxData is clocked in using TxCLK and then
synchronized to REFCLK and transmitted to the twisted-pair. The RxData is synchronized to the
RxCLK. See
Figure 23 on page 141
.
Figure 19. Intel
LXT9785/LXT9785E Serial MII Receive Synchronization
Table 44. Intel
LXT9785/LXT9785E RX Status Encoding Bit Definitions
Signal
Definition
CRS
Carrier Sense - identical to MII, except that it is not an asynchronous signal.
RxDV
Receive Data Valid - identical to MII. When RX_DV = 0, status
information is transmitted to the MAC. When RX_DV = 1,
received data is transmitted to the MAC.
0 = Status Byte
1 = Valid Data Byte
RxER
(RxData0)
Inter-frame status bit RxData0 indicates whether or not the
PHY detected an error somewhere in the previous frame.
0 = No Error
1 = Error
SPEED
(RxData1)
Inter-frame status bit RxData1 indicates port operating speed.
0 = 10 Mbps
1 = 100 Mbps
DUPLEX
(RxData2)
Inter-frame status bit RxData2 indicates port duplex condition.
0 = Half-duplex
1 = Full-duplex
LINK
(RxData3)
Inter-frame status bit RxData3 indicates port link status.
0 = Down
1 = Up
JABBER
(RxData4)
Inter-frame status bit RxData4 indicates port jabber status.
0 = OK
1 = Error
VALID
(RxData5)
Inter-frame status bit RxData5 conveys the validity of the upper
nibble of the last byte of the previous frame
0 = Invalid
1 = Valid
False Carrier
(RxData6)
Inter-frame status bit RxData6 indicates whether or not the
PHY has detected a false carrier event.
0 = No FC detected
1 = FC detected
RxData7
This bit is set to 1.
1 = Always
1. Both RxData0 and RxData5 bits are valid in the segment immediately following a frame, and remain valid
until the first data segment of the next frame begins.
CRS
RX_DV
RXD0
RXER
RXD1
Speed
RXD2
Duplex
RXD3
Link
RXD4
Jabber
RXD5
Valid
RXD6
FCE
RXD7
RXD7
CRS
CLOCK
RxSYNC
RX