Non-DMA Mode
12-16
ADSP-BF535 Blackfin Processor Hardware Reference
The
THRE
flag is set when
UARTx_THR
is ready for new data and cleared
when the processor loads new data into
UARTx_THR
. Writing
UARTx_THR
when it is not empty overwrites the register with the new value and the
previous character is never transmitted.
The
DR
flag signals when new data is available in
UARTx_RBR
. This flag is
cleared automatically when the processor reads from
UARTx_RBR
. Reading
UARTx_RBR
when it is not full returns the previously received value.
With interrupts disabled, these status flags can be polled to determine
when data is ready to move. Note that because polling is processor inten-
sive, it is not typically used in real-time signal processing environments.
Alternatively, UART writes and reads can be accomplished by ISRs. Both
UART devices feature independent interrupt channels. In non-DMA
mode, the UART TX interrupt channel is not used. All interrupt sources
within one UART device share the same interrupt request, the UART RX
interrupt channel. As controlled by
UARTx_IER
, this interrupt can be raised
by any of the following:
• THR Empty (
THRE
) event
• RBR Full (
DR
) event
• Modem Status event
• Receive Error condition
The ISR can evaluate the Status bit field within the UARTx Interrupt
Identification register (
UARTx_IIR
) to determine the exact interrupt
source. Interrupts also must be assigned and unmasked by the
ADSP-BF535 processor’s interrupt controller.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...