Functional Overview
3.13.10.1 Receiver Buffer Register (RBR)
The UART receiver section consists of a receiver shift register (RSR) and a RBR. The RBR is actually a 16-byte
FIFO. Timing is supplied by the 16
×
receiver clock. Receiver section control is a function of the UART line control
register.
The UART RSR receives serial data from SIN. The RSR then concatenates the data and moves it into the RBR
FIFO. In the TL16C450 mode, when a character is placed in the RBR and the received data available interrupt
is enabled (IER0 = 1), an interrupt is generated. This interrupt is cleared when the data is read out of the RBR.
In the FIFO mode, the interrupts are generated based on the control setup in the FIFO control register.
3.13.10.2 Scratch Register
The scratch register is an 8-bit register that is intended for the programmer’s use as a scratchpad in the sense
that it temporarily holds the programmer’s data without affecting any other UART operation.
3.13.10.3 Transmitter Holding Register (THR)
The UART transmitter section consists of a THR and a transmitter shift register (TSR). The THR is actually a
16-byte FIFO. Transmitter section control is a function of the UART line control register.
The UART THR receives data off the internal data bus and when the shift register is idle, moves it into the TSR.
The TSR serializes the data and outputs it at SOUT. In the TL16C450 mode, if the THR is empty and the
transmitter holding register empty (THRE) interrupt is enabled (IER1 = 1), an interrupt is generated. This
interrupt is cleared when a character is loaded into the register. In the FIFO mode, the interrupts are generated
based on the control setup in the FIFO control register.
3.14 General-Purpose I/O Pins
In addition to the standard BIO and XF pins, the 5407/5404 has pins that can be configured for
general-purpose I/O. These pins are:
•
•
16 McBSP pins — BCLKX0/1, BCLKR0/1, BDR0/1/2, BFSX0/1, BFSR0/1, BDX0/1/2, BCLKRX2,
BFSRX2
8 HPI data pins — HD0–HD7
The general-purpose I/O function of these pins is only available when the primary pin function is not required.
3.14.1
McBSP Pins as General-Purpose I/O
When the receive or transmit portion of a McBSP is in reset, its pins can be configured as general-purpose
inputs or outputs. For more details on this feature, see Section 3.8.
3.14.2
HPI Data Pins as General-Purpose I/O
The 8-bit bidirectional data bus of the HPI can be used as general-purpose input/output (GPIO) pins when the
HPI is disabled (HPIENA = 0) or when the HPI is used in HPI16 mode (HPI16 = 1). Two memory-mapped
registers are used to control the GPIO function of the HPI data pins — the general-purpose I/O control register
(GPIOCR) and the general-purpose I/O status register (GPIOSR). The GPIOCR is shown in Figure 3–23.
15
Reserved
0
7
DIR7
R/W-0
DIR6
R/W-0
DIR5
R/W-0
4
DIR4
R/W-0
3
DIR3
R/W-0
DIR2
R/W-0
DIR1
R/W-0
0
DIR0
R/W-0
8
LEGEND:
R = Read, W = Write,
n = value after reset
Figure 3–23. General-Purpose I/O Control Register (GPIOCR) [MMR Address 003Ch]
November 2001 – Revised July 2003
SPRS007B
47
TI [ TEXAS INSTRUMENTS ]
