MPC8321E Freescale Semiconductor, Inc, MPC8321E Datasheet - Page 76

• Manufacturer Part Number: MPC8321E
• Description: Mpc8321e Powerquicc Ii Pro Processor
• Manufacturer: Freescale Semiconductor, Inc

System Design Information
output impedance is the average of two components, the resistances of the pull-up and pull-down devices.
When data is held high, SW1 is closed (SW2 is open) and R
OV
other in value. Then, Z
The value of this resistance and the strength of the driver’s current source can be found by making two
measurements. First, the output voltage is measured while driving logic 1 without an external differential
termination resistor. The measured voltage is V
while driving logic 1 with an external precision differential termination resistor of value R
measured voltage is V
R
Table 65
nominal OV
76
term
MPC8323E PowerQUICC™ II Pro Integrated Communications Processor Family Hardware Specifications, Rev. 1
DD
× (V
/2. R
Note: Nominal supply voltages. See
Impedance
Differential
summarizes the signal impedance targets. The driver impedance are targeted at minimum V
1
P
/V
R
R
DD
then becomes the resistance of the pull-up devices. R
N
P
2
, 105°C.
– 1). The drive current is then I
Control, Configuration, Power
2
Local Bus, Ethernet, DUART,
0
= (1/(1/R
= (R
P
Management
+ R
42 Target
42 Target
Figure 45. Driver Impedance Measurement
1
Data
NA
N
+ 1/R
Table 65. Impedance Characteristics
)/2.
Table
2
)) × I
1, T
j
1
source
= 105°C.
source
= R
source
. Solving for the output impedance gives R
= V
25 Target
25 Target
PCI
NA
1
× I
/R
P
Pad
source
R
R
source
is trimmed until the voltage at the pad equals
N
P
OGND
OV
DD
P
. Second, the output voltage is measured
.
DDR DRAM
and R
20 Target
20 Target
SW2
SW1
NA
N
are designed to be close to each
Symbol
Z
DIFF
Z
Z
0
0
Freescale Semiconductor
term
Unit
W
W
W
. The
source
=
DD
,