AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 161

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

11
11.1
Figure 11-1
CHAPTER
Int.
Bus
PROGRAMMABLE I/O PINS
OVERVIEW
Thirty-two pins on the Am186ES and Am188ES microcontrollers are available as user-
programmable I/O signals (PIOs). Each of these pins can be used as a PIO if the normal
function of the pin is not needed. If a pin is enabled to function as a PIO signal, the normal
function is disabled and does not affect the pin. A PIO signal can be configured to operate
as an input or output with or without internal pullup or pulldown resistors, or as an open-
drain output.
After power-on reset, the PIO pins default to various configurations. The column titled
Power-On Reset State in Table 11-1 lists the defaults for the PIOs. The system initialization
code must reconfigure 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.
Programmable I/O Pin Operation
Normal
Data In
PDATA
WR
PDATA
RD
D
Q
OE
Q
Programmable I/O Pins
Normal
Function
D
40 MHz
(CLK)
Mode
Dir.
PIO
Mode
1
0
PIO
Direction
Data In
VCC
PIOTRI
PIOPULL
PIODRV
Pin
11-1