MPC8640 and MPC8640D Integrated Host Processor Hardware Specifications, Rev. 3
70
Freescale Semiconductor
PCI Express
Maximum time to
transition to a
valid electrical
idle after sending
an electrical idle
ordered set
TTX-IDLE-SET-TO-IDLE
—
20
UI
After sending an electrical idle ordered set, the
transmitter must meet all electrical idle specifications
within this time. This is considered a debounce time for
the transmitter to meet electrical idle after transitioning
from L0.
Maximum time to
transition to valid
Tx specifications
after leaving an
electrical idle
condition
TTX-IDLE-TO-DIFF-DATA
—
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
Differential
Return Loss
RLTX-DIFF
12
—
dB
Measured over 50 MHz to 1.25 GHz. See Note 4
Common Mode
Return Loss
RLTX-CM
6
—
dB
Measured over 50 MHz to 1.25 GHz. See Note 4
DC Differential
TX Impedance
ZTX-DIFF-DC
80
100
120
Ω
TX DC differential mode low impedance
Transmitter DC
Impedance
ZTX-DC
40
—
Ω
Required TX D+ as well as D– DC impedance during
all states
Lane-to-Lane
Output Skew
LTX-SKEW
—
500 +
2 UI
ps
Static skew between any two transmitter lanes within a
single link
AC Coupling
Capacitor
CTX
75
—
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.
Crosslink
Random
Timeout
Tcrosslink
0
—
1
ms
This random timeout helps resolve conflicts in crosslink
configuration by eventually resulting in only one
downstream and one upstream port. See Note 7.
Notes:
1. No test load is necessarily associated with this value.
2. Specified at the measurement point into a timing and voltage compliance test load as shown in
Figure 52 and measured over
any 250 consecutive Tx UIs. (Also refer to the transmitter compliance eye diagram shown in
Figure 50)3. A TTX-EYE = 0.70 UI provides for a total sum of deterministic and random jitter budget of TTX-JITTER-MAX = 0.30 UI for the
transmitter collected over any 250 consecutive Tx UIs. The TTX-EYE-MEDIAN-to-MAX-JITTER median is less than half of the total
TX jitter budget collected over any 250 consecutive Tx UIs. It should be noted that the median is not the same as the mean.
The jitter median describes the point in time where the number of jitter points on either side is approximately equal as opposed
to the averaged time value.
4. The transmitter input impedance shall result in a differential return loss greater than or equal to 12 dB and a common mode
return loss greater than or equal to 6 dB over a frequency range of 50 MHz to 1.25 GHz. This input impedance requirement
applies to all valid input levels. The reference impedance for return loss measurements is 50
Ω to ground for both the D+ and
D– line (that is, as measured by a Vector Network Analyzer with 50
Ω probes—see
Figure 52). Note that the series capacitors
CTX is optional for the return loss measurement.
5. Measured between 20–80% at transmitter package pins into a test load as shown in Figure 52 for both VTX-D+ and VTX-D–. 6. See Section 4.3.1.8 of the PCI Express Base Specifications Rev 1.0a
7. See Section 4.2.6.3 of the PCI Express Base Specifications Rev 1.0a
8. MPC8640D SerDes transmitter does not have CTX built-in. An external AC coupling capacitor is required.
Table 49. Differential Transmitter Output Specifications (continued)
Parameter
Symbol
Min
Nom
Max
Units
Notes