Bidirectional Pin Buffers - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

Signal Routing Unit

Bidirectional Pin Buffers

All peripherals within the DAI that have bidirectional pins generate a cor-
responding pin enable signal. Typically, the settings within a peripheral's
Control registers determine if a bidirectional pin is an input or an output,
and is then is driven accordingly. Both the peripherals Controls registers
and the configuration of the SRU can effect the direction of signal flow in
a pin buffer.
For example, from an external perspective, when a serial port (SPORT) is
completely routed off-chip, it uses four pins—clock, frame sync, data
channel A, and data channel B. Because all four of these pins comprise the
interface that the serial port presents to the SRU, there is a total of 12 con-
nections as shown in
Figure 12-9. SRU Connections for SPORTx
For each bidirectional line, the serial port provides three separate signals.
For example, a SPORT clock has three separate SRU connections—an
input clock to the SPORT (
SPORT (
SPORTx_CLK_O
12-12
Figure 12-9.
SPORT0_CLK_I
SPORT0_CLK_O
SPORT0_CLK_PBEN_O
SPORT0_FS_I
SPORT0_FS_O
SPORT0_FS_PBEN_O
SPORT0_DA_I
SPORT0_DA_O
SPORT0_DA_PBEN_O
SPORT0_DB_I
SPORT0_DB_O
SPORT0_DB_PBEN_O
SPORTx_CLK_I
), and an output enable from the SPORT
ADSP-2126x SHARC Processor Hardware Reference
Interface
to SRU
), an output clock from the