
ADSP-BF59x Blackfin Processor Hardware Reference
11-11
UART Port Controllers
Interrupt Processing
Each UART module has three interrupt outputs. One is dedicated for
transmission, one for reception, and the third is used to report line status.
As shown in
Figure 11-1 on page 11-3
, the transmit and receive requests
are routed through the DMA controller. The status request goes directly
to the system interrupt controller after being ORed with interrupt signals
from other modules.
If the associated DMA channel is enabled, the request functions as a DMA
request. If the DMA channel is disabled, it simply forwards the request to
the system interrupt controller. Note that a DMA channel must be associ-
ated with the UART module to enable TX and RX interrupts. Otherwise,
the transmit and receive requests cannot be forwarded. Refer to the
description of the peripheral map registers in the
Direct Memory Access
chapter.
Transmit interrupts are enabled by the
ETBEI
bit in the
UART_IER
register.
If set, the transmit request is asserted when the
THRE
bit in the
UART_LSR
register transitions from 0 to 1, indicating that the TX buffer is ready for
new data.
Note that the
THRE
bit resets to 1. When the
ETBEI
bit is set in the
UART_IER
register, the UART module immediately issues an interrupt or
DMA request. In this way, no special handling of the first character is
required when transmission of a string is initiated. Simply set the
ETBEI
bit and let the interrupt service routine load the first character from mem-
ory and write it to the
UART_THR
register in the normal manner.
Accordingly, the
ETBEI
bit can be cleared if the string transmission has
completed. For more information, see
“DMA Mode” on page 11-17
.
The
THRE
bit is cleared by hardware when new data is written to the
UART_THR
register. These writes also clear the TX interrupt request. How-
ever, they also initiate further transmission. If software doesn’t want to
continue transmission, the TX request can alternatively be cleared by
either clearing the
ETBEI
bit or by reading the
UART_IIR
register.
Summary of Contents for ADSP-BF59x Blackfin
Page 64: ...Development Tools 1 22 ADSP BF59x Blackfin Processor Hardware Reference...
Page 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
Page 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Page 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Page 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...