Table 5-6. Input-Output Usage (Continued)
Input/Output with
Internal
Pullup Resistors
Required
External
Resistor
750FX Signal
Name
Input/
Output
Active Level
Usage Group
Level Protect
Comments
Notes
DH[0:31]
High
High
High
Low
Low
—
Input/Output
Input/Output
Input/Output
Input
Data Bus
Data Bus
Keeper
Keeper
1, 3, 4
1, 3, 4
DL[0:31]
DP[0:7]
DRTRY
GBL
Keeper
Keeper
3, 4
Input/Output
—
Transfer Attributes
Power Supply
Interrupt/Resets
Interrupt/Resets
LSSD
1, 3, 4
GND
HRESET
INT
Low
Low
High
High
Low
Low
—
Input
Keeper
Keeper
Active driver
2, 3, 4, 5
Input
Active driver or pullup
3, 4, 5
L1_TSTCLK
L2_TSTCLK
LSSD_MODE
MCP
Input
Not enabled
Not enabled
Not enabled
5K Ω
5K Ω
5K Ω
Pullup/pulldown, as required
5
Input
LSSD
Pullup required to OV
Pullup required to OV
Active driver or pullup
5
5
DD
DD
Input
LSSD
Input
Interrupt/Resets
Power Supply
Clock Control
Keeper
3, 4, 5
OV
—
DD
PLL_CFG[0:4]
PLL_RNG[0:1]
QACK
High
High
Low
Low
Low
Low
Low
Input
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
As required Pullup/pulldown, as required
As required Pullup/pulldown, as required
Must be actively driven
3, 4, 5
3, 4, 5
3, 4, 5
3, 4, 5
3, 4, 5
3, 4
Input
Input
Control
QREQ
Output
Output
Input
Status/Control
Chip actively drives
RSRV
No connect
SMI
SRESET
Notes:
Input
Interrupt/Resets
Active driver or pullup
2, 3, 4, 5
1. Depends on the system design. The electrical characteristics of the 750FX do not add additional constraints to the system design, so whatever is done with the net will depend on the system require-
ments.
2. HRESET, SRESET, and TRST are signals used for ESP and RISCWatch to enable proper operation of the debuggers. Logical AND gates should be placed between these signals and PowerPC
750FX RISC Microprocessor. (Refer to Figure 5-7 on page 48.)
3. The 750FX provides protection from meta-stability on inputs through the use of a “keeper” circuit on specific inputs. Refer to Level Protection on page 48 for a more detailed description.
4. If a system design requires a signal level to be maintained while not being actively driven, an external resistor or device must be used (Keepers assure no meta-stability of inputs but do not guarantee
a level).
5. The 750FX does not require external pullups on address and data lines. Control lines must be treated individually.
IBM [ IBM ]
