AMD Geode LX 800@0.9W - Manual (Page 23)

AMD Geode™ LX Processors Data Book 23
Signal Definitions 33234H
3.1 Buffer Types
The Ball Assignment tables starting on page 26 include a
column labeled “Buffer Type”. The details of each buffer
type listed in this column are given in Table 3-2. The col-
umn headings in Table 3-2 are identified as follows:
TS: Indicates whether the buffer may be put into the TRI-
STATE mode. Note some pins that have buffer types that
allow TRI-STATE may never actually enter the TRI-STATE
mode in practice, since they may be inputs or provide other
signals that are always driven. To determine if a particular
signal can be put in the TRI-STATE mode, consult the indi-
vidual signal descriptions in Section 3.4 "Signal Descrip-
tions" on page 33.
OD: Indicates if the buffer is open-drain, or not. Open-drain
outputs may be wire ORed together and require a discrete
pull-up resistor to operate properly.
5VT: Indicates if the buffer is 5-volt tolerant, or not. If it is 5-
volt tolerant, then 5 volt TTL signals may be safely applied
to this pin.
PU/PD: Indicates if an internal, programmable pull-up or
pull-down resistor may be present.
Current High/Low (mA): This column gives the current
source/sink capacities when the voltage at the pin is high,
and low. The high and low values are separated by a “/”
and values given are in milli-amps (mA).
Rise/Fall @ Load: This column indicates the rise and fall
times for the different buffer types at the load capacitance
indicated. These measurements are given in two ways:
rise/fall time between the 20%-80% voltage levels, or, the
rate of change the buffer is capable of, in volts-per-nano-
second (V/ns).
Note the presence of “Wire” type buffer in this table. Sig-
nals identified as a wire-type are not driven by a buffer,
hence no rise/fall time or other measurements are given;
these are marked “NA” in Table 3-2. The wire-type connec-
tion indicates a direct connection to internal circuits such
as power, ground, and analog signals.
Table 3-2. Buffer Type Characteristics
Name TS OD 5VT PU/PD
Current
High/Low
(mA) Rise/Fall @ Load
24/Q3 X X 24/24 3 ns @ 50 pF
24/Q5 X X 24/24 5 ns @ 50 pF
24/Q7 X X 24/24 7 ns @ 50 pF
5V X X 16/16 1.25V/ns @ 40 pF
PCI X 0.5/1.5 1-4V/ns @ 10 pF
DDRCLK 10/10 8.5V/ns @ 15 pF
DDR 2.4V/ns @ 50 pF
Wire NA NA NA NA NA