AM186EM-33VCSLASHW datasheet(50/98 Pages) AMD

50 / 98 page

Am186/188EM and Am186/188EMLV Microcontrollers

PRELIMINA R Y

PROGRAMMABLE I/O (PIO) PINS

There are 32 pins on the Am186EM and Am188EM mi-

crocontrollers that are available as user multipurpose

signals. Table 2 and Table 3 on page 30 list the PIO

pins. Each of these pins can be used as a user-pro-

grammable input or output signal if the normal shared

function is not needed.

If a pin is enabled to function as a PIO signal, the pre-

assigned signal function is disabled and does not affect

the level on the pin. A PIO signal can be configured to

operate as an input or output with or without a weak

pullup or pulldown, or as an open-drain output.

After power-on reset, the PIO pins default to various

configurations. The column titled

Power-On Reset Sta-

tus in Table 2 and Table 3 on page 30 lists the defaults for

the PIOs. The system initialization code must reconfigure

the PIOs as required.

The A19–A17 address pins default to normal operation

on power-on reset, allowing the processor to correctly

begin fetching instructions at the boot address

FFFF0h. The DT/R, DEN, and SRDY pins also default to

normal operation on power-on reset.

Note that emulators use A19, A18, A17, S6, and UZI.

If the AD15–AD0 bus override is enabled on power-on

reset, then S6/CLKDIV2 and UZI revert to normal opera-

tion instead of PIO input with pullup. If BHE/ADEN (186)

or RFSH2/ADEN (188) is held Low during power-on reset

the AD15–AD0 bus override is enabled.

AM186EM-33VC/W Scheda tecnica(PDF) 50 Page - Advanced Micro Devices