
14-22
MCF5407 User’s Manual
UART Module Signal Denitions
An internal interrupt request signal (IRQ) is provided to notify the interrupt controller of an
interrupt condition. The output is the logical NOR of unmasked UISRn bits. The interrupt
level of a UART module is programmed in the interrupt controller in the system integration
module (SIM). The UART can use the autovector for the programmed interrupt level or
supply the vector from the UIVRn when the UART interrupt is acknowledged.
The interrupt level, priority, and auto-vectoring capability is programmed in SIM register
Note that the UARTs can also automatically transfer data by using the DMA rather than
interrupting the core. When UIMR[FFULL] is 1 and a receiver’s FIFO is full, it can send
an interrupt to a DMA channel so the FIFO data can be transferred to memory. Note also
that UART0 and UART1’s interrupt requests are connected to DMA channel 2 and
channel 3, respectively.
NOTE:
The terms ‘assertion’ and ‘negation’ are used to avoid
confusion between active-low and active-high signals.
‘Asserted’ indicates that a signal is active, independent of the
voltage level; ‘negated’ indicates that a signal is inactive.
Figure 14-25 shows a signal conguration for a UART/RS-232 interface.
Table 14-18. UART Module Signals
Signal
Description
Transmitter
Serial Data
Output (TxD)
In UART mode, TxD is held high (mark condition) when the transmitter is disabled, idle, or operating
in the local loop-back mode. Data is shifted out on TxD on the falling edge of the clock source, with
the least signicant bit (lsb) sent rst. For UART1 in modem mode, TxD is held low when the
transmitter is disabled or idle. Data is shifted out on TxD on the rising edge of the clock signal driving
UART1’s CTS input. UART1 transfers can be specied as either lsb or msb rst.
Receiver
Serial Data
Input (RxD)
Data received on RxD is sampled on the rising edge of the clock source, with the lsb received rst.
For UART1 in modem mode, data received on RxD is sampled on the falling edge of the clock signal
driving UART1’s CTS input. UART1 transfers can be specied as either lsb or msb rst.
Clear-to-
Send (CTS)
This input can generate an interrupt on a change of state. For UART1 in modem mode, CTS must be
driven by the serial bit clock from the external CODEC or AC ‘97 controller.
Request-to-
Send (RTS)
This output can be programmed to be negated or asserted automatically by either the receiver or the
transmitter. When connected to a transmitter’s CTS, RTS can control serial data ow. For UART1 in
AC ‘97 mode, RTS serves as the frame sync or start-of-frame (SOF) output to the external AC ‘97
controller. When this mode is used, the AC ‘97 BIT_CLK, which is input on CTS, is divided by 256.
Timer Input
(TIN1)
When UART1 in modem mode is used as an 8- or 16-bit CODEC interface, TIN1 must be driven by
the frame sync or SOF output from the external CODEC. SOF is sampled on the falling edge of the
bit clock driving CTS. TIN1 can still be used in all timer modes except capture mode when UART1 is
being used as an 8- or 16-bit CODEC interface. See
Table 14-26.