CS5535-UDCF AMD (ADVANCED MICRO DEVICES), CS5535-UDCF Datasheet - Page 159

• Manufacturer Part Number: CS5535-UDCF
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of CS5535-UDCF

• Operating Temperature (min): 0C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

General Purpose Input/Output
5.15
Proper use and understanding of the General Purpose
Input/Output (GPIO) subsystem is the key to applying the
Geode CS5535 companion device in a custom system
design. By totalizing the optional features of the Geode
CS5535 companion device GPIOs, system functions such
as soft buttons, DDC monitoring, timers, system interrupts,
and others, may be implemented. The system designer
should pay careful attention to the suite of features avail-
able through the GPIO subsystem and, because the
GPIOs are multiplexed with other on-chip functions, must
make careful trade-offs to obtain the features desired in the
system.
The register space for control of the GPIO subsystem con-
tains space for control of 32 GPIOs. Since only 28 GPIOs
are realized, the control bits for the non-existent
GPIO[31:29], and GPIO[23] are marked “Reserved”.
GPIO[22:16] are multiplexed with the LPC bus; therefore, if
the system requires an LPC bus, GPIO[22:16] are not
available as GPIOs. Likewise, GPIO[15:14] are multiplexed
with the SMB (System Management Bus); if the system
requires the SMB, GPIO[15:14] will be dedicated to this
function and not available as GPIOs. Other GPIOs are mul-
tiplexed with individual functions as indicated in Table 3-8
"GPIO Options" on page 47.
Features
• Input Features:
• Output Features:
AMD Geode™ CS5535 Companion Device Data Book
— Each of the available GPIOs may be configured as
— Each of the available 28 GPIOs has a configurable
— As indicated in Table 3-8 "GPIO Options" on page
an input. A block of eight Input Conditioning Func-
tions, providing edge detection, event counting, and
input filtering, may be configured for use by any eight
of the 28 GPIOs, though all 28 may have edge detec-
tion. The optionally-conditioned input may then be
fed to steering logic that can connect it to an inter-
rupt, or power-management input event (PME).
output cell. The output cell for each GPIO may be
independently configured to provide a variety of inter-
face options. The cell may be enabled or disabled,
configured as a totem-pole or open-drain type, have
internal pull-up or pull-down resistors applied, or be
inverted.
47, the GPIOs have differing output driver types and
reset defaults. When choosing a GPIO for a given
function, choose one with a compatible output driver
type, and one that the use of, does not make another
desired function inaccessible. Careful study of this
table will assist the system designer in making proper
selections of the desired functionality of the suite of
GPIOs.
General Purpose Input/Output
• Auxiliary Functions:
• Output Mapping:
• Power Domains:
• Auto-sense:
• Recommended Functions:
— Most of the 28 GPIOs have additional hard-wired
— After passing through the optional input conditioning
— The GPIO circuits are distributed into the Working
— GPIO5 and GPIO6 have a feature called Auto-sense.
— System designers at AMD have created a list of
internally-connected functions that may be selected
by choosing either the AUX_1 or AUX_2 outputs.
Use of these allows internal functions to be accessed
at the device pins. Table 3-8 "GPIO Options" on page
47 identifies these auxiliary functions, including
access to the UARTS and multi-function timers, as
well as certain power-management controls.
circuits, any GPIO may be mapped (connected) to
one of eight PIC-level interrupts, or to one of eight
Power Management Event (PME) inputs. A given
GPIO may not be simultaneously mapped to both an
interrupt and a PME. The PIC subsystem interrupt
inputs may be configured to cause the generation of
an ASMI-type interrupt from any or all of the mapped
GPIO signals.
and Standby power domains. Those circuits in the
Standby power domain may be used for system
wakeup events, since they remain powered when the
Working power is removed. As indicated in Table 3-8
"GPIO Options" on page 47, GPIO[28:24] are located
in the Standby power domain; all others are in the
Working power domain. Event/Filter pairs 6 and 7 are
located in the Standby domain; pairs [5:0] are in the
Working power domain.
When reset is applied to the system, a weak internal
pull-up is applied to the pad. When reset is de-
asserted, the auto-sense value is used to establish
the pull-up/down state on the de-assertion edge. If
nothing pulls down the pad, then the weak pull-up
continues to be applied. If the pad is pulled down,
then pull-up is set to “no” and pull-down is set to
“yes”. The output driver does not actively drive the
pad, that is, it remains in TRI-STATE mode. If an
auto-sensed pull-down is desired, a diode between
the reset signal and the GPIO pin will pull it down
during the auto-sense operation but will have no
effect during normal operation.
recommended uses for selected GPIOs, see Table 3-
8 "GPIO Options" on page 47. The desired functions
were matched up with GPIOs by selecting appro-
priate buffer types and multiplexing options to create
an optimal list of recommended uses for the GPIOs.
Designers may use these recommended functions as
a starting point and make modifications to the list as
needed to fit the particulars of their system.
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