SC16C752IB48 datasheet(7/47 Pages) PHILIPS

7 / 47 page

Philips Semiconductors

SC16C752

Dual UART with 64-byte FIFO

Product data

Rev. 04 — 20 June 2003

7 of 47

9397 750 11635

The SC16C752 has selectable hardware ﬂow control and software ﬂow control.

Hardware ﬂow control signiﬁcantly reduces software overhead and increases system

efﬁciency by automatically controlling serial data ﬂow using the RTS output and CTS

input signals. Software ﬂow control automatically controls data ﬂow by using

programmable Xon/Xoff characters.

The UART includes a programmable baud rate generator that can divide the timing

reference clock input by a divisor between 1 and (216

− 1).

6.1 Trigger levels

The SC16C752 provides independent selectable and programmable trigger levels for

both receiver and transmitter DMA and interrupt generation. After reset, both

transmitter and receiver FIFOs are disabled and so, in effect, the trigger level is the

default value of one byte. The selectable trigger levels are available via the FCR. The

programmable trigger levels are available via the TLR.

6.2 Hardware ﬂow control

Hardware ﬂow control is comprised of Auto-CTS and Auto-RTS. Auto-CTS and

Auto-RTS can be enabled/disabled independently by programming EFR[7:6].

With Auto-CTS, CTS must be active before the UART can transmit data.

Auto-RTS only activates the RTS output when there is enough room in the FIFO to

receive data and de-activates the RTS output when the RX FIFO is sufﬁciently full.

The halt and resume trigger levels in the TCR determine the levels at which RTS is

activated/deactivated.

If both Auto-CTS and Auto-RTS are enabled, when RTS is connected to CTS, data

transmission does not occur unless the receiver FIFO has empty space. Thus,

overrun errors are eliminated during hardware ﬂow control. If not enabled, overrun

errors occur if the transmit data rate exceeds the receive FIFO servicing latency.

Fig 3.

Autoﬂow control (Auto-RTS and Auto-CTS) example.

FIFO

SERIAL-TO-

PARALLEL

FLOW

CONTROL

FIFO

PARALLEL-

TO-SERIAL

FLOW

CONTROL

PARALLEL-

TO-SERIAL

FLOW

CONTROL

SERIAL-TO-

PARALLEL

FLOW

FIFO

UART 1

UART 2

D7-D0

RTS

CTS

RTS

D7-D0

CONTROL

002aaa228

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