Texas Instruments TMS320C3x 사용자 설명서

Serial Ports

12-41

Peripherals

Figure 12–32. Variable Continuous Mode Without Frame Sync

CLKX/R

FSR/FSX (external)

FSX (internal)

DX/DR

A1

AN

B1

BN

C1

C2

XINT
RINT

Load DXR with D

read DRR

Set

R/XFS

M

DXR loaded

with B

XINT

DXR loaded

with A

XINT
RINT

Load DXR with C

read DRR

R/XVAREN = 1

R/XFSM = 1

The serial ports are controlled through memory-mapped registers on the dedi-
cated peripheral bus. A general procedure for initializing and/or reconfiguring
the serial ports follows.

1) Halt the serial port by clearing the XRESET and/or RRESET bits of the serial-

port global-control register. To do this, write a 0 to the serial-port global-
control register. The serial ports are halted on RESET.

2) Configure the serial port via the serial-port global-control register (with

XRESET = RRESET = 0) and the FSX/DX/CLKX and FSR/DR/CLKR port-
control registers. If necessary, configure the receive/transmit registers;
timer control (with XHLD = RHLD = 0), timer counter, and timer period.
Refer to section 12.2.14 for more information.

3) Start the serial-port operation by setting the XRESET and RRESET bits

of the serial-port global-control register and the XHLD and RHLD bits of
the serial-port receive/transmit timer-control register, if necessary.

In addition to the examples presented in this section, you can find DMA/serial
port initialization examples in Example 12–9 and Example 12–10 on pages
12-76 and 12-77, respectively.