SBPH400-3 データシートの表示（PDF） - STMicroelectronics
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SBPH400-3 Datasheet PDF : 43 Pages
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SBPH400-3
The SBPH400 has control over the bidirectional pins. It will, upon request, transfer this control
to the link device, which can then drive these pins. The 8 bidirectional data pins D[0:7] form
the data bus. The portion of the D bus which carries packet data is left-justified starting with
the 0 bit. Packet data for 100 Mb/s transfers uses D[0:1], 200 Mb/s transfers use D[0:3], and
400 Mb/s transfers use D[0:7]. The unused D[n] signals are transmitted as ‘0’ and are ignored
when the link device has control of the bus. The control bus CTL[0:1] carries the control
information. The LREQ pin is used by the link device to request access to the serial bus and
to read and write the chip registers.
2.8.2 Types of operation
The four basic operations which may occur at the PHY-Link interface are: request, status,
transmit and receive. Request is the only operation initiated by the link layer device. The link
layer device uses the request operation to read or write a register located in the SBPH400 or
to request the bus so that the SBPH400 can initiate a transmit action on the bus. The
SBPH400 initiates a receive action whenever a packet is received from the serial bus and a
status indication to notify events to the link layer device.
2.8.3 Control pins
When the SBPH400 has control of the PHY-Link interface the CTL[0:1] lines are encoded as
shown in Table 2.5.
Table 2.5
CTL[0:1]
00
01
10
11
CTL[0:1] When the SBPH400 is driving
NAME
Idle
Status
Receive
Grant
DESCRIPTION
No activity (default mode)
The SBPH400 is sending status information to the link device
An incoming packet is being transferred from the SBPH400 to the link
device
The link device is granted the bus to send a packet
When the link layer device has been granted the PHY-Link interface by the SBPH400, it should
encode the CTL[0:1] lines Table 2.6
Table 2.6
00
01
10
11
CTL[0:1] when the link is driving (upon grant from SBPH400)
NAME
Idle
Hold
Transmit
unused
DESCRIPTION
The link device has released the bus (normally after transmission).
Note that multiple Idles may need to be transmitted.
The link device is preparing data or wishes to reacquire the bus without
arbitrating to send another packet
The link device is sending a packet to the SBPH400
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