SC16C554BIB64 PHILIPS [NXP Semiconductors], SC16C554BIB64 Datasheet - Page 16

• Manufacturer Part Number: SC16C554BIB64
• Description: 5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 16-byte FIFOs
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 13133
Product data sheet
D7 to D0
Fig 7. Autoflow control (auto-RTS and auto-CTS) example
6.4.1 Auto-RTS (see
6.4.2 Auto-CTS (see
6.4 Autoflow control (see
Autoflow control is comprised of auto-CTS and auto-RTS. With auto-CTS, the CTS input
must be active before the transmitter FIFO can emit data. With auto-RTS, RTS becomes
active when the receiver needs more data and notifies the sending serial device. When
RTS is connected to CTS, data transmission does not occur unless the receiver FIFO has
space for the data; thus, overrun errors are eliminated using UART 1 and UART 2 from a
SC16C554B/554DB with the autoflow control enabled. If not, overrun errors occur when
the transmit data rate exceeds the receiver FIFO read latency.
Auto-RTS data flow control originates in the receiver timing and control block (see block
diagrams in
level. When the receiver FIFO level reaches a trigger level of 1, 4, or 8 (see
is de-asserted. With trigger levels of 1, 4, and 8, the sending UART may send an
additional byte after the trigger level is reached (assuming the sending UART has another
byte to send) because it may not recognize the de-assertion of RTS until after it has
begun sending the additional byte. RTS is automatically reasserted once the RX FIFO is
emptied by reading the receiver buffer register. When the trigger level is 14 (see
Figure
the RX line. RTS is reasserted when the RX FIFO has at least one available byte space.
The transmitter circuitry checks CTS before sending the next data byte. When CTS is
active, it sends the next byte. To stop the transmitter from sending the following byte, CTS
must be released before the middle of the last stop bit that is currently being sent (see
Figure
is enabled, CTS level changes do not trigger host interrupts because the device
automatically controls its own transmitter. Without auto-CTS, the transmitter sends any
data present in the transmit FIFO and a receiver overrun error may result.
FIFO
FIFO
RCV
XMT
ACE1
10), RTS is de-asserted after the first data bit of the 16th character is present on
8). The auto-CTS function reduces interrupts to the host system. When flow control
SERIAL TO
PARALLEL
TO SERIAL
PARALLEL
CONTROL
CONTROL
Figure 1
FLOW
FLOW
Figure
Figure
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 16-byte FIFOs
and
Rev. 01 — 9 February 2005
CTS
RTS
RX
TX
Figure
7)
7)
Figure
2) and is linked to the programmed receiver FIFO trigger
7)
TX
CTS
RX
RTS
SC16C554B/554DB
TO SERIAL
SERIAL TO
PARALLEL
PARALLEL
CONTROL
CONTROL
FLOW
FLOW
ACE2
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
FIFO
FIFO
XMT
RCV
002aaa048
Figure
9), RTS
D7 to D0
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