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TI486 Microprocessor - Al Kossow's Bitsavers

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Electrical Connections<br />

5.1 Electrical Connections<br />

5.1.1 Power and Ground Connections and Decoupling<br />

5.1.2 Pullup/Pulidown Resistors<br />

Due to the high frequency operation of the T1486, it is necessary to install and<br />

test this device using standard high-frequency techniques. The high clock<br />

frequencies used in the <strong>TI486</strong> and its output buffer circuits can cause transient<br />

power surges when several output buffers switch output levels simultaneously.<br />

These effects can be minimized by filtering the dc power leads with<br />

low-inductance decoupling capacitors, using low-impedance wiring, and by<br />

connecting all of the Vee and GND (V SS) pins. There are 14 Vee and 18 Vss<br />

pins on the 100-pin quad flat package, and 20 Vee and 21 VSS pins on the<br />

132-pin pin grid array package.<br />

Table 5-1 lists the input pins that are internally connected to pullup and<br />

pulldown resistors (See Figure 5-1). The pullup resistors are connected to<br />

Vee and the pulldown resistors are connected to V ss. When unused, these<br />

inputs do not require connection to external pullup or pulldown resistors.<br />

Table 5-1. Pins Connected to Internal Pullup and Pulldown Resistors<br />

Figure 5-1. Internal PulluplPulldown-IV Characteristic<br />

60<br />

SIGNAL<br />

<strong>TI486</strong>SLC/E<br />

PIN<br />

<strong>TI486</strong>DLC/E<br />

PIN<br />

RESISTOR<br />

A20M 31 F13 pullup<br />

BUSY 34 B9 pullup<br />

ERROR 36 A8 pullup<br />

FLT 28 - pullup<br />

FLUSH 30 E13 pullup<br />

KEN 29 B12 pullup<br />

PEREa 37 C8 pulldown<br />

SMI 47 C7 pullup<br />

SUSP 43 A4 pullup<br />

50<br />

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