UART Serial Ports
21-6
Élan™SC520 Microcontroller User’s Manual
For each UART, six handshaking signals are provided:
■
DTRx (Data Terminal Ready) output—When the signal is Low, it informs the modem set
that the UART is ready to establish a communications link. The DTRx output signal can
be asserted and deasserted by the UART x Modem Control (UARTxMCR) register.
Loopback mode operation holds DTRx in its inactive state.
■
DSRx (Data Set Ready) input—When the signal is Low, it indicates that the modem is
ready to establish the communications link with the UART. The state of the DSRx pin
can be tested in the UART x Modem Status (UARTxMSR) register. The DDSR status
bit provided in the UART x Modem Status (UARTxMSR) register indicates if the DSRx
signal has changed state since the register was last read. An interrupt can also be
generated upon DSRx change.
■
RTSx (Request-to-Send) output—When the signal is Low, it informs the modem that the
UART is ready to exchange data. The RTSx output signal can be asserted and
deasserted by the UART x Modem Control (UARTxMCR) register. Loopback mode
operation holds RTSx in its inactive state.
■
CTSx (Clear-to-Send) input—When the signal is Low, it indicates that the modem is
ready to exchange data. The state of the CTSx pin can be tested in the UART x Modem
Status (UARTxMSR) register. The DCTS status bit in the UART x Modem Status
(UARTxMSR) register indicates if the CTSx signal has changed state since the register
was last read. An interrupt can also be generated upon CTSx change.
■
DCDx (Data Carrier Detect) input—When the signal is Low, it indicates that the data
carrier has been detected by the modem and that contact between it and the other
modem is established. The state of the DCDx pin can be tested in the UART x Modem
Status (UARTxMSR) register. The DDCD status bit in the UART x Modem Status
(UARTxMSR) register indicates if the DCDx signal has changed state since the register
was last read. An interrupt can also be generated upon DCDx change.
■
RINx (Ring Indicator) input—When the signal is Low, it indicates that a telephone ringing
signal has been received by the modem. The state of the RINx pin can be tested in the
UART x Modem Status (UARTxMSR) register. The TERI status bit is also provided in
the UART x Modem Status (UARTxMSR) register indicates if the RINx signal has
changed state from asserted to deasserted since the register was last read. An interrupt
can also be generated upon RINx deassertion.
21.5.1
Data Transmission
21.5.1.1
16450-Compatible UART Mode
In 16450-compatible (non-FIFO or character) mode:
1. Data written to the UART x Transmit Holding (UARTxTHR) register is subsequently
latched into the internal transmitter shift register when the transmitter shift register is
empty.
2. Once data has been latched into the internal transmitter shift register, the Transmit
Holding Register Empty (THRE) bit in the UART x Line Status (UARTxLSR) register
goes to 1 (optionally generating a UART interrupt).
3. The application is once again permitted to write data to the UART x Transmit Holding
(UARTxTHR) register.
Note that writing to the UART x Transmit Holding (UARTxTHR) register in this mode when
the THRE bit is not set can result in incorrect data being transmitted.
Содержание Elan SC520
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Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...