Intel 440GX - Manual (Page 103)

Intel
®
440GX AGPset Design Guide 4-3
Debug Recommendations
The extra loading of the LAI562 requires stronger pull-up values on the target system. However,
due to the current limitations of some signal drivers, this stronger value may not be feasible.
Calculation of the correct pull-up resistor value for each of the CMOS signals should include a load
analysis based on the pull-up voltage, pull-up voltage tolerance, pull-up resistor tolerance, V
IH and
V IL specifications, driver current rating, input current leakage, input timings, etc. The resulting
values may conflict.
As a result of the extra loading the following compromise pull-ups to Vcc 2.5 are recommended.
The actual value required by your system may vary depending on the logic connected and the drive
strength of the signal to the Slot 1 connector.
Inputs to the Slot 1 connector from the ITP562 Port:
• PREQ# 150 - 330 ohm
• TDI 150 - 330 ohm
• TMS, TCK 1 Kohm
• TRST# 470 - 680 ohm (A pull-down is recommended but a pull-up may
be used)
Inputs to the Slot 1 connector from the PIIX4E:
• STPCLK# 430 ohm
• SMI# 430 ohm
• SLP# 150 - 330 ohm
Outputs from the Slot 1 connector:
• TDO 150 ohm
• THERMTRIP# 150 - 220 ohm
• FERR# 150 - 220 ohm
Figure 4-1. LAI Probe Input Circuit