DSP56303 datasheet(190/292 Pages) FREESCALE

190 / 292 page

DSP56303 User’s Manual, Rev. 2

8-22

Freescale Semiconductor

Serial Communication Interface (SCI)

addresses. If SCKP is set and SSHTD is set, SCI Synchronous mode is equivalent to the SSI

operation in 8-bit data on-demand mode.

Note:

When data is written to a peripheral device, there is a two-cycle pipeline delay until

any status bits affected by this operation are updated. If you read any of those status

bits within the next two cycles, the bit does not reflect its current status. For details see

the DSP56300 Family Manual.

8.7 GPIO Signals and Registers

Three registers control the GPIO functionality of the SCI pins: Port E control register (PCRE),

Port E direction register (PRRE) and Port E data register (PDRE).

8.7.1 Port E Control Register (PCRE)

The read/write PCRE controls the functionality of SCI GPIO signals. Each of the PCRE[2–0] bits

controls the functionality of the corresponding port signal. When a PCRE[i] bit is set, the

corresponding port signal is configured as an SCI signal. When a PC[i] bit is cleared, the

corresponding port signal is configured as a GPIO signal. A hardware RESET signal or a software

RESET instruction clears all PCRE bits.

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

9876543210

PE2/

SCLK

PE1/

TXD

PE0/

RXD

Note:

For bits 2–0, a 0 selects PEn as the signal and a 1 selects the specified SCI signal.

= Reserved. Read as zero. Write to zero for future compatibility.

Figure 8-8. Port E Control Register (PCRE X:$FFFF9F)

DSP56303 Datasheet(PDF) 190 Page - Freescale Semiconductor, Inc