Pin Buffers As Signal Input Pins - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

Pin Buffers as Signal Input Pins

When the DAI pin is to be used only as an input, connect the correspond-
ing pin buffer enable to logic low as shown in
the buffer amplifier and allows an off-chip source to drive the value pres-
ent on the DAI pin and at the pin buffer output. When the pin buffer
enable (
PBENxx_I
the signal driven onto the DAI pin by an external source, and the pin buf-
fer input (
PBxx_I
PIN BUFFER
OUTPUT
PIN BUFFER
INPUT
(NOT USED)
INTERFACE
TO SRU
PIN BUFFER
ENABLE
(= LOW)
Figure 12-8. Pin Buffer as Input
Although not strictly necessary, it is recommended programming practice
to tie the pin buffer input to logic low whenever the pin buffer enable is
tied to logic low. By default, the pin buffer enables are connected to
SPORT pin enable signals that may change value. Tying the pin buffer
input low decouples the line from irrelevant signals and can make code
simpler to debug. It also ensures that no voltage is driven by the pin if a
bug in your code accidentally asserts the pin enable.
ADSP-2126x SHARC Processor Hardware Reference
) is cleared (= 0), the pin buffer output (
) is not used.
PBxx_O
PAD
PBxx_I
DRIVER
IN
PIN
ENABLE
PINENxx_I
Digital Audio Interface
Figure 12-8. This disables
PBxx_O
EXTERNAL
PACKAGE
CONNECTION
PBxx_O
OUT
) will be
PIN
12-11