Description of Operation
13-6
ADSP-BF537 Blackfin Processor Hardware Reference
When enabled by the
ETBEI
bit in the
UARTx_IER
register, a 0 to 1 transi-
tion of the
THRE
flag requests an interrupt on the dedicated
TXREQ
output.
This signal is routed through the DMA controller. If the associated DMA
channel is enabled, the
TXREQ
signal functions as a DMA request, other-
wise the DMA controller simply forwards it to the SIC interrupt
controller.
The
UARTx_THR
register and the internal
TSR
register can be seen as a
two-stage transmit buffer. When data is pending in either one of these reg-
isters, the
TEMT
flag is low. As soon as the data has left the
TSR
register, the
TEMT
bit goes high again and indicates that all pending transmit operation
has finished. At that time it is safe to disable the
UCEN
bit or to three-state
off-chip line drivers.
UART Receive Operation
The receive operation uses the same data format as the transmit configura-
tion, except that one valid stop bit is always sufficient, that is, the
STB
bit
has no impact to the receiver.
After detection of the start bit, the received word is shifted into the inter-
nal shift register (
RSR)
at a bit rate of
SCLK/(16 x Divisor)
. Once the
appropriate number of bits (including one stop bit) is received, the con-
tent of the
RSR
register is transferred to the
UARTx_RBR
registers, shown in
. Finally, the data ready (
DR
) bit and the status flags are
updated in the
UARTx_LSR
register, to signal data reception, parity, and
also error conditions, if required.
The
RSR
and the
UARTx_RBR
registers can be seen as a two-stage receive
buffer. If more than 2 bytes are received before software reads the
UARTx_RBR
register, an overrun error is reported and old data is
overwritten.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...