Intel E3845 FH8065301487715 Data Sheet
Product codes
FH8065301487715
SIO – High Speed UART
Intel
®
Atom™ Processor E3800 Product Family
4176
Datasheet
The processor can also check transmitter empty LSR.TEMT, which is set when the
Transmit FIFO or Holding register is empty.
Transmit FIFO or Holding register is empty.
27.3.2.3
Autoflow Control
Autoflow Control uses Clear-to-Send (nCTS) and Request-to-Send (nRTS) signals to
automatically control the flow of data between the UART and external modem. When
autoflow is enabled, the remote device is not allowed to send data unless the UART
asserts nRTS low. If the UART de-asserts nRTS while the remote device is sending data,
the remote device is allowed to send one additional byte after nRTS is deasserted. An
overflow could occur if the remote device violates this rule. Likewise, the UART is not
allowed to transmit data unless the remote device asserts nCTS low. This feature
increases system efficiency and eliminates the possibility of a Receive FIFO Overflow
error due to long interrupt latency.
automatically control the flow of data between the UART and external modem. When
autoflow is enabled, the remote device is not allowed to send data unless the UART
asserts nRTS low. If the UART de-asserts nRTS while the remote device is sending data,
the remote device is allowed to send one additional byte after nRTS is deasserted. An
overflow could occur if the remote device violates this rule. Likewise, the UART is not
allowed to transmit data unless the remote device asserts nCTS low. This feature
increases system efficiency and eliminates the possibility of a Receive FIFO Overflow
error due to long interrupt latency.
Autoflow mode can be used in two ways: Full autoflow, automating both nCTS and
nRTS, and half autoflow, automating only nCTS. Full Autoflow is enabled by writing a 1
to bits 1 and 5 of the Modem Control Register (MCR). Auto-nCTS-Only mode is enabled
by writing a 1 to bit 5 and a 0 to bit 1 of the MCR register.
nRTS, and half autoflow, automating only nCTS. Full Autoflow is enabled by writing a 1
to bits 1 and 5 of the Modem Control Register (MCR). Auto-nCTS-Only mode is enabled
by writing a 1 to bit 5 and a 0 to bit 1 of the MCR register.
27.3.2.4
RTS (UART Output)
When in full autoflow mode, nRTS is asserted when the UART FIFO is ready to receive
data from the remote transmitter. This occurs when the amount of data in the Receive
FIFO is below the programmable threshold value. When the amount of data in the
Receive FIFO reaches the programmable threshold, nRTS is de-asserted. It will be
asserted once again when enough bytes are removed from the FIFO to lower the data
level below the threshold.
data from the remote transmitter. This occurs when the amount of data in the Receive
FIFO is below the programmable threshold value. When the amount of data in the
Receive FIFO reaches the programmable threshold, nRTS is de-asserted. It will be
asserted once again when enough bytes are removed from the FIFO to lower the data
level below the threshold.
27.3.2.5
CTS (UART Input)
When in Full or Half-Autoflow mode, nCTS is asserted by the remote receiver when the
receiver is ready to receive data from the UART. The UART checks nCTS before sending
the next byte of data and will not transmit the byte until nCTS is low. If nCTS goes high
while the transfer of a byte is in progress, the transmitter will complete this byte.
receiver is ready to receive data from the UART. The UART checks nCTS before sending
the next byte of data and will not transmit the byte until nCTS is low. If nCTS goes high
while the transfer of a byte is in progress, the transmitter will complete this byte.
27.4
Register Map
for additional information.