![](http://datasheet.mmic.net.cn/100000/IBM25PPC750FX-DB0122T_datasheet_3492262/IBM25PPC750FX-DB0122T_46.png)
Datasheet
DD
2.X
PowerPC
750FX
RISC
Microprocessor
Preliminary
5.
System
Design
Information
Page
44
of
63
Body_750FX_DS_DD2.X.fm.2.0
June
9,
2003
Table 5-6. Input-Output Usage
750FX Signal
Name
Active Level
Input/
Output
Usage Group
Input/Output with
Internal
Pullup Resistors
Level Protect
Required
External
Resistor
Comments
Notes
A1VDD
—
Power Supply
A2VDD
—
Power Supply
A[0:31]
High
Input/Output
Address Bus
Keeper
1, 3, 4
AACK
Low
Input
Address Termination
Keeper
Must be actively driven
3, 4, 5
ABB
Low
Input/Output
Keeper
5K
Pullup required to OVDD
3, 4, 5
AGND
—
Power Supply
AP[0:3]
High
Input/Output
Keeper
3, 4
ARTRY
Low
Input/Output
Address Termination
Keeper
5K
Pullup required to OVDD
3, 4, 5
BG
Low
Input
Address Arbitration
Keeper
Active driver or pulldown
3, 4, 5
BR
Low
Output
Address Arbitration
Keeper
Chip actively drives
3, 4, 5
BVSEL
N/A
Input
Input/Output Level
5K
Pullup/pulldown, as required
5
CHECKSTOP
Low
Output
Interrupt/Resets
Keeper
5K
Pullup required to OVDD
3, 4, 5
CI
Low
Output
Transfer Attributes
Keeper
1, 3, 4
CKSTP_IN
Low
Input
Interrupt/Resets
Keeper
Must be actively driven
3, 4, 5
CLK_OUT
High
Output
Keeper
3, 4
DBB
Low
Input/Output
Keeper
5K
Pullup required to OVDD
3, 4, 5
DBDIS
Low
Input
Keeper
3, 4
DBG
Low
Input
Data Arbitration
Keeper
Active driver or tie low
3, 4, 5
DBWO
Low
Input
Keeper
3, 4
Notes:
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
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.