PD1394P11ABD 查看數據表（PDF） - Philips Electronics
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PD1394P11ABD Datasheet PDF : 20 Pages
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Philips Semiconductors
3-port physical layer interface
Preliminary specification
PDI1394P11A
22.0 TRANSMIT
When the link wants to transmit information, it will first request
access to the bus through the LREQ pin. Once the phy receives this
request, it will arbitrate to gain control of the bus. When the phy wins
ownership of the serial bus, it will grant the bus to the link by
asserting the ‘transmit’ state on the CTL pins for at least one
SYSCLK cycle, followed by idle for one clock cycle.
The link will take control of the bus by asserting either ‘hold’ or
‘transmit’ on the CTL lines. ‘hold’ is used by the link to keep control
of the bus if it needs some time to prepare the data for transmission.
The phy will keep control of the bus for the link by asserting a
‘data-prefix’ state on the bus. It is not necessary for the link to use
‘hold’ if it is ready to transmit as soon as bus ownership is granted.
When the link is prepared to send data, it will assert ‘transmit’ on the
CTL lines as well as sending the first four bits of the packet on the
D[0:3] lines (assuming 200 Mb/s). The ‘transmit’ state is held on the
CTL pins until the last bits of data have been sent. The link will then
assert ‘Idle’ on the CTL lines for one clock cycle after which it
releases control of the interface.
However, there will be times when the link will need to send another
packet without releasing the bus. For example, the link may want to
send consecutive isochronous packets or it may want to attach a
response to an acknowledgment. To do this, the link will assert ‘hold’
22.1 TRANSMIT TIMING WAVEFORMS
instead of ‘Idle’ when the first packet of data has been completely
transmitted. ‘Hold’, in this case, informs the phy that the link needs
to send another packet without releasing control of the bus. The phy
will then wait a set amount of time before asserting ‘transmit’. The
link can then proceed with the transmittal of the second packet. After
all data has been transmitted and the link has asserted ‘Idle’ on the
CTL pins, the phy will assert its own ‘Idle’ state on the CTL lines.
When sending multiple packets in this fashion, it is required that all
data be transmitted at the same speed. This is required because the
transmission speed is set during arbitration and since the arbitration
step will be skipped, there will be no way of informing the network of
a change in speed.
The PDI1394P11A includes a digital camera/single port Phy
interoperability enhancement. When a node is root (and
consequently cycle master) and is sending Isochronous data, it does
not need to arbitrate for the bus (by default it would win any such
arbitration). This fact was overlooked by some early 100 Mbps
single port Phy manufacturers whose chips are too slow to handle
the absence of the arbitration time. This causes their Phys to see a
header CRC error and the packet to be discarded. The
PDI1394P11A compensates for this by extending the Data_Prefix
time before sending the packet. This makes the PDI1394P11A fully
compatible with all existing 100 Mbps Phys on the market.
PHY
CTL [0:1]
00
11
00
ZZ
ZZ
ZZ
ZZ
ZZ
ZZ
ZZ
ZZ
00
PHY
D [0:3]
0000 0000 0000 ZZZZ
ZZZZ ZZZZ ZZZZ ZZZZ
ZZZZ ZZZZ ZZZZ 0000
LINK
CTL [0:1]
ZZ
ZZ
ZZ
01
01
10
10
10
10
00
00
ZZ
LINK
D [0:3]
ZZZZ ZZZZ ZZZZ 0000
0000
P0
P1
P2
Pn
0000 0000 ZZZZ
PHY
CTL [0:1]
PHY
D [0:3]
LINK
CTL [0:1]
LINK
CTL [0:1]
ZZ
ZZ
ZZ
ZZ
00
ZZZZ ZZZZ ZZZZ ZZZZ 0000
10
10
01
00
ZZ
Pn–1
Pn
0000 0000 ZZZZ
00
11
00
ZZ
0000 0000 0000 ZZZZ
ZZ
ZZ
ZZ
01
ZZZZ ZZZZ ZZZZ 0000
ZZ
ZZ
ZZ
ZZZZ ZZZZ ZZZZ
01
10
10
0000
P0
P1
NOTE:
ZZ = High Impedance State
P0 ⇒ Pn = Packet Data
NOTE:
ZZ = High Impedance State
P0 => Pn = Packet data
Figure 10. Transmit Timing Waveforms
SV00235
1999 Mar 10
17
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