![Marvell PXA300 Скачать руководство пользователя страница 113](http://html.mh-extra.com/html/marvell/pxa300/pxa300_developers-manual_1734615113.webp)
69rlq62d-f714peg4 * Memec (Headquar
ter
s) - Unique
Tec
h,
Insight,
Impact
MAR
VELL CONFIDENTIAL,
UNDER ND
A# 12101050
69rlq62d-f714peg4 * Memec (Headquar
ter
s) - Unique
Tec
h,
Insight,
Impact
MAR
VELL CONFIDENTIAL,
UNDER ND
A# 12101050
69r
lq62d-f714peg4 * Memec (Headquar
ters) - Unique
T
ech, Insight, Impact * UNDER ND
A# 12101050
MAR
VELL CONFIDENTIAL - UNA
UTHORIZED DISTRIB
UTION OR USE STRICTL
Y PR
OHIBITED
Copyright © 2006 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006, Preliminary
Document Classification: Proprietary Information
Page 113
Not approved by Document Control. For review only.
(3) Bits 4:6 are present only when a pin has been defined as potentially waking up on an edge. If the device is not
configured in this manner, the registers are not present and writing to them has no effect.
4.8
Multi-Function Pin Block Diagram
The multi-function pin has a relatively simple function. Several logical functions are connected via a multiplexer
to a single pin and one is selected via MFPR xx[AF_SEL]. Each logical function consists of some or all of the
following:
•
Data-out signal
•
Output-enable signal
•
Input signal
•
Pullup control
•
Pulldown control
An alternate function can be an output, an input, or a bidirectional function. Any function that is not selected is
disconnected logically from the pins both for input AND output (the output signals being ignored and the input
signals being forced to a default state as they are fed to the internal device).
Note:
The pin direction is controlled by hardware in all cases. In effect, the configuration of the
alternate function connects the pin to its driving logic and that logic is responsible for
determining whether the pin is an input or an output. For a GPIO function, the direction is
controlled by the GPIO function (that is, the direction register).
For output, a pin can be set to drive a 0, 1, pull high or pull low, or to maintain a three-state condition. Each
option can be selected dynamically, allowing functions such as drive 0 and pull high.
Multiple pins can be allocated to the same function, the output data and enable signals being duplicated, and the
input signals being OR’ed together (or NANDed if active low) to form a single function. Software is responsible
for avoiding situations where multiple pins are assigned to the same function (or if this situation is preferred, to
manage the configurations).
4.8.1
Example
A single pin can be defined as having two alternate functions, in this case a UART data input and an SSP data-out
signal.
The SSP pin can drive 0 or 1, or three-state. It has no data input. The UART function has no data output
(therefore, it is, in effect, a three-state) but does have a data input. SSP is function 0 and UART is function 1.
Function 0 has the data-out and the output-enable connections connected to the SSP, but the data-input
connections are not used. Function 1 has the output-enable connection set to a 0 (forcing the output to be a
three-state), and the data output unconnected. The data input is connected to the UART.
When function 0 is selected, the output pin follows the SSP signals. The data-enable output from the UART is
ignored and the data input is forced to be a 0 (the standard default case). When Function 1 is selected, the SSP
outputs are ignored, the output is three-state, and the input connected to the UART. This configuration raises the
issue of potentially floating inputs if some device is not always driving the input.