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Enhanced Synchronous Serial Interface (ESSI)
7.6 GPIO Signals and Registers
The functionality of each ESSI port is controlled by three registers: port control register (PCRC,
PCRD), port direction register (PRRC, PRRD), and port data register (PDRC, PDRD).
7.6.1 Port Control Registers (PCRC and PCRD)
The read/write 24-bit PCRs control the functionality of the signal lines for ESSI0 and ESSI1.
Each of the PCR bits 5–0 controls the functionality of the corresponding signal line. When a
PCR[i] bit is set, the corresponding port signal is configured as an ESSI signal. When a PCR[i]
bit is cleared, the corresponding port signal is configured as a GPIO signal. Either a hardware
signal or a software RESET instruction clears all PCR bits.
RESET
23
22
21
11
10
9
Note:
For Px[5–0], a 0 selects Pxn as the signal and a 1 selects the specified ESSI signal. For ESSI0, the GPIO signals are
PC[5–0] and the ESSI signals are STD0, SRD0, SCK0, and SC0[2–0]. For ESSI1, the GPIO signals are PD[5–0] and
the ESSI signals are STD1, SRD1, SCK1, and SC1[2–0].
= Reserved. Read as zero. Write with zero for future compatibility.
Figure 7-18. Port Control Registers (PCRC X:$FFFFBF) (PCRD X:$FFFAF)
7.6.2 Port Direction Registers (PRRC and PRRD)
The read/write PRRC and PRRD control the data direction of the ESSI0 and ESSI1 GPIO signals
when they are enabled by the associated Port Control Register (PCRC or PCRD, respectively).
When PRRC[i] or PRRD[i] is set, the corresponding signal is an output (GPO) signal. When
PRRC[i] or PRRD[i] is cleared, the corresponding signal is an input (GPI) signal. Either a
hardware
signal or a software RESET instruction clears all PRRC and PRRD bits.
RESET
23
22
21
11
10
9
Note:
For bits 5–0, a 0 configures PRxn as a GPI and a 1 configures PRxn as a GPO. For ESSI0, the GPIO signals are
PC[5–0]. For ESSI1, the GPIO signals are PD[5–0]. The corresponding direction bits for Port C GPIOs are PRC[5–0].
The corresponding direction bits for Port D GPIOs are PRD[5–0].
= Reserved. Read as zero. Write with zero for future compatibility.
Figure 7-19. Port Direction Registers (PRRC X:$FFFFBE) (PRRD X: $FFFFAE)
7-34
20
19
18
8
7
6
20
19
18
8
7
6
DSP56311 User's Manual, Rev. 2
17
16
15
5
4
3
PCx5
PCx4
PCx3
17
16
15
5
4
3
PRx5
PRx4
PRx3
14
13
12
2
1
0
PCx2
PCx1
PCx0
14
13
12
2
1
0
PRx2
PRx1
PRx0
Freescale Semiconductor
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