Table 5-6. Input/Output Use (Sheet 3 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
No resistor by
design
SYSCLK
High
Input
Clock Control
Keeper
Keeper
Active driver
3, 4, 5
3, 4, 5
TA
Low
High
Low
Input
Input
Data Termination
Active driver
TBEN
TBST
Input/Output
Transfer Attributes
JTAG
Keeper
1, 3, 4
5
External
pulldown
TCK
High
Input
Not enabled
Enabled high
5k Ω to GND
50 μA at 2.5 V
25 μA at 1.8 V
(the pullup current for the inter-
nal resistor)
Internal
enabled
TDI
High
Input
JTAG
5
TDO
High
Low
Low
Output
Input
JTAG
Data Termination
Control
Keeper
Keeper
Keeper
3, 4
3, 4, 5
3, 4
TEA
Active driver or pullup
Must be actively driven
TLBISYNC
Input
50 μA at 2.5 V
25 μA at 1.8 V
(the pullup current for the inter-
nal resistor)
Internal
enabled
TMS
High
Low
Input
Input
JTAG
JTAG
Enabled high
Enabled high
5
50 μA at 2.5 V
25 μA at 1.8 V
(the pullup current for the inter-
nal resistor)
Internal
enabled
TRST
2, 5
TS
Low
Input/Output
Output
Address Start
Keeper
Keeper
5k Ω
Pullup required to OVDD
3, 4, 5
1, 3, 4
TSIZ[0:2]
Notes:
High
Transfer Attributes
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 ]
