Table 5-6. Input/Output Use (Sheet 1 of 4)
750FL Micropro-
Input/
Input/Output with
Internal
Pullup Resistors
Required
External
Resistor
cessor Signal
Name
Active Level
Usage Group
Level Protect
Comments
Notes
Output
A1VDD
Power Supply
Power Supply
A2VDD
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
Pullup required to OVDD
Input/Output
5k Ω
5k Ω
AGND
AP[0:3]
ARTRY
BG
Power Supply
High
Low
Low
Low
N/A
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 OVDD
Active driver or pulldown
Chip actively drives
BR
Output
Input
BVSEL
CHECKSTOP
CI
5k Ω
5k Ω
Pullup/pulldown, as required
Pullup required to OVDD
Low
Low
Low
High
Low
Low
Low
Low
Output
Output
Input
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
Keeper
3, 4, 5
1, 3, 4
3, 4, 5
3, 4
Transfer Attributes
Interrupt/Resets
CKSTP_IN
CLK_OUT
DBB
Must be actively driven
Pullup required to OVDD
Active driver or tie low
Output
Input/Output
Input
5k Ω
3, 4, 5
3, 4
DBDIS
DBG
Input
Data Arbitration
3, 4, 5
3, 4
DBWO
Notes:
Input
1. Depends on the system design. The electrical characteristics of the 750FL microprocessor do not add additional constraints to the system design. Therefore, whatever is
done with the net depends on the system requirements.
2. HRESET, SRESET, and TRST are signals used for ESP and RISCWatch to enable the correct operation of the debuggers. Logical AND gates must be placed between
these signals and 750FL microprocessor. (See Figure 5-7 IBM RISCWatch JTAG to HRESET, TRST, and SRESET Signal Connector on page 55.)
3. The 750FL microprocessor provides protection from metastability on inputs through the use of a “keeper” circuit on specific inputs. See Section 5.5 Level Protection on
page 55 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 metastability of
inputs but do not guarantee a level).
5. The 750FL microprocessor does not require external pullups on address and data lines. Control lines must be treated individually.
IBM [ IBM ]
