MC72000 Freescale Semiconductor, MC72000 Datasheet - Page 54

• Manufacturer Part Number: MC72000
• Description: Integrated Bluetooth Radio
• Manufacturer: Freescale Semiconductor

Hardware Functional Description
7.2.4.1 RTS — Request to Send
This input is used to control the transmitter. By asserting RTS, the far-end device signals to the UART that
it is ready to receive. Normally, the transmitter waits until this signal is active (low) before a character is
transmitted. If the Flow Control Enable (FCE) bit is disabled, the transmitter sends a character whenever a
character is ready to transmit. When flow control is enabled, the RTS signal can be configured to either stop
a transmission upon assertion or to enable a transmission upon deassertion.
7.2.4.2 CTS — Clear to Send
This output is used to control the transmitter of the remote device. Normally, the receiver indicates that it is
ready to receive data by asserting this pin (low). When enabled, this signal is controlled by the watermarks
in the RXFIFO.
7.2.4.3 Transmitter
The transmitter accepts a parallel character and transmits it serially. When the transmitter is enabled, the
start, stop, and parity (if enabled) bits are added to the character. RTS is used to flow-control the serial data
if desired. If RTS is negated (high), the transmitter finishes sending the character in progress (if any) then
stops and waits for RTS to again become asserted (low).
7.2.4.4 Receiver
The receiver accepts a serial data stream and converts it into a parallel character.When enabled, it searches
for a start bit, qualifies it, then samples the succeeding data bits at the bit-center. Jitter tolerance and noise
immunity are provided by sampling at a 16x rate and using voting techniques to clean up the samples. Once
the start bit has been found, the data bits, parity bit (if enabled), and stop bits are shifted in. If parity is
enabled, it is checked and its status is reported in the USTAT register. Similarly, frame errors and breaks
are checked and reported. If the CTS_LEVEL is set to zero, the receiver ready interrupt flag (RXRDY) will
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Overrun Error — An error condition in which the latest character received is ignored to prevent
overwriting an already existing character in the UART Receiver Buffer. An overrun error indicates
that the software reading the buffer is not keeping up with the actual reception of characters on the
RXD line.
NOTE:
MC71000
RXD
RTS
TXD
CTS
The above signals assume control (FCe) = 0 (enabled and control) and
(FCp) = 0 (active low RTS/CTS signals).
Freescale Semiconductor, Inc.
For More Information On This Product,
MC72000 Advance Information Data Sheet
Figure 32. General UART Connection
Go to: www.freescale.com
Preliminary
Remote
RXD
CTS
RTS
TXD
MOTOROLA