Table 5-6. Input-Output Usage
Input/Output with
Internal
Pullup Resistors
Required
External
Resistor
750FX Signal
Active Level
Name
Input/
Output
Usage Group
Level Protect
Comments
Notes
A1V
A2V
—
—
—
Power Supply
Power Supply
DD
DD
—
A[0:31]
AACK
ABB
High
Low
Low
—
Input/Output
Input
Address Bus
Keeper
Keeper
Keeper
1, 3, 4
3, 4, 5
3, 4, 5
Address Termination
Must be actively driven
Input/Output
—
5K Ω
5K Ω
Pullup required to OV
DD
AGND
AP[0:3]
ARTRY
BG
Power Supply
High
Low
Low
Low
N/A
Low
Low
Low
High
Low
Low
Low
Low
Input/Output
Input/Output
Input
Keeper
Keeper
Keeper
Keeper
3, 4
3, 4, 5
3, 4, 5
3, 4, 5
5
Address Termination
Address Arbitration
Address Arbitration
Input/Output Level
Interrupt/Resets
Pullup required to OV
DD
Active driver or pulldown
Chip actively drives
BR
Output
Input
BVSEL
CHECKSTOP
CI
5K Ω
5K Ω
Pullup/pulldown, as required
Output
Output
Input
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Pullup required to OV
3, 4, 5
1, 3, 4
3, 4, 5
3, 4
DD
Transfer Attributes
Interrupt/Resets
CKSTP_IN
CLK_OUT
DBB
Must be actively driven
Output
Input/Output
Input
5K Ω
Pullup required to OV
3, 4, 5
3, 4
DD
DBDIS
DBG
Input
Data Arbitration
Active driver or tie low
3, 4, 5
3, 4
DBWO
Notes:
Input
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 ]
