PCI Express
Table 52. Differential Transmitter (TX) Output Specifications (continued)
Symbol
Parameter
Min
Nom
Max
Unit
Comments
T
Minimum time
spent in
electrical idle
50
—
UI Minimum time a transmitter must be in electrical
idle utilized by the receiver to start looking for an
electrical idle exit after successfully receiving an
electrical idle ordered set
TX-IDLE-MIN
T
Maximum time
to transition to a
valid electrical
idle after
sending an
electrical idle
ordered set
—
—
—
—
20
UI After sending an electrical idle ordered set, the
transmitter must meet all electrical idle
TX-IDLE-SET-TO-IDLE
specifications within this time. This is considered
a debounce time for the transmitter to meet
electrical idle after transitioning from L0.
T
Maximum time
to transition to
valid TX
specifications
after leaving an
electrical idle
condition
20
UI Maximum time to meet all TX specifications when
transitioning from electrical idle to sending
differential data. This is considered a debounce
time for the TX to meet all TX specifications after
leaving electrical idle
TX-IDLE-TO-DIFF-DATA
RL
Differential
return loss
12
6
—
—
—
—
dB Measured over 50 MHz to 1.25 GHz.
See Note 4.
TX-DIFF
RL
Common mode
return loss
dB Measured over 50 MHz to 1.25 GHz.
See Note 4.
TX-CM
Z
DC differential
TX impedance
80
40
—
75
100
—
120
—
Ω
TX DC differential mode low impedance
TX-DIFF-DC
Z
Transmitter DC
impedance
Ω
Required TX D+ as well as D– DC impedance
during all states
TX-DC
L
Lane-to-lane
output skew
—
500
+ 2 UI
ps Static skew between any two transmitter lanes
within a single Link
TX-SKEW
C
AC coupling
capacitor
—
200
nF All transmitters shall be AC coupled. The AC
coupling is required either within the media or
within the transmitting component itself. See note
8.
TX
MPC8548E PowerQUICC™ III Integrated Processor Hardware Specifications, Rev. 6
Freescale Semiconductor
71
FREESCALE [ Freescale ]
