Motorola DSP56301 - Manual (Page 261)

GPIO Signals and Registers
Serial Communication Interface (SCI) 8 -25
8.7.2 Port E Direction Register (PRRE)
The read/write PRRE controls the direction of SCI GPIO signals. When port signal[i] is
configured as GPIO, PRRE[i] controls the port signal direction. When PRRE[i] is set, the
GPIO port signal[i] is configured as output. When PRRE[i] is cleared, the GPIO port signal[i]
is configured as input. A hardware
RESET signal or a software RESET instruction clears all
PRRE bits.
8.7.3 Port E Data Register (PDRE)
Bits 2–0 of the read/write 24-bit PDRE writes data to or reads data from the associated SCI
signal lines when configured as GPIO signals. If a port signal PE[i] is configured as an input
(GPI), the corresponding PDRE[i] bit reflects the value present on the input signal line. If a
port signal PE[i] is configured as an output (GPO), a value written to the corresponding
PDRE[i] bit is reflected as a value on the output signal line. Either a hardware
RESET signal
or a software RESET instruction clears all PDR bits.
23 22 21 20 19 18 17 16 15 14 13 12
11 10 9 8 7 6 5 4 3 2 1 0
PRRE2 PRRE1 PRRE0
Note: For bits 2–0, a 0 configures PEn as a GPI and a 1 configures PEn as a GPO. For the SCI, the GPIO signals
are PE[2–0]. The corresponding direction bits for Port E GPIOs are PRRE[2–0].
= Reserved. Read as zero. Write with zero for future compatibility.
Figure 8-9. Port E Direction Register (PRRE X:$FFFF9E)
23 22 21 20 19 18 17 16 15 14 13 12
11 10 9 8 7 6 5 4 3 2 1 0
PDRE2 PDRE1 PDRE0
Note: For bits 2–0, the value represents the level that is written to or read from the associated signal line if enabled
as a GPIO signal by the PCRE bits. For SCI, the GPIO signals are PE[2–0]. The corresponding data bits
are PDRE[2–0].
= Reserved. Read as zero. Write with zero for future compatibility.
Figure 8-10. Port Data Registers (PDRE X:$FFFF9D)