SC28L201 Datasheet, PDF (47/110 Pages) NXP Semiconductors – 3.3 V, 5 V UART, 3.125 Mbit/s, with 256-byte FIFO

Philips Semiconductors
SC28L201
3.3 V, 5 V UART, 3.125 Mbit/s, with 256-byte FIFO
Table 18: MR2 - Mode Register 2 (address 0x22) bit description …continued
Bit Symbol Description
5
Tx Controls RTS. Transmitter Request-to-Send Control.
This bit controls the deactivation of the RTSN output (I/O2) by the transmitter.
This output is manually asserted and negated by appropriate commands
issued via the command register. MR2[5] = 1 negates (drives to logical 1)
RTSN automatically one bit time after the characters in the transmit shift
register and in the TxFIFO (if any) are completely transmitted (includes the
programmed number of stop bits if the transmitter is not enabled). This
feature can be used to automatically terminate the transmission of a
message as follows:
• Program Auto Reset mode: MR2[5] = 1.
• Enable transmitter.
• Assert RTSN via command.
• Send message.
• Verify the next-to-last character of the message is being sent by waiting
until transmitter ready is asserted. Disable transmitter after the last
character is loaded into the TxFIFO.
• The last character will be transmitted and RTSN will be reset one bit
time after the last stop bit.
Remark: When the transmitter controls the RTSN pin, the meaning of the pin
is completely changed. It has nothing to do with the normal RTSN/CTSN
‘handshaking’. It is usually used to mean ‘end of message’ and to ‘turn the
line around’ in simplex communications. From a practical point of view, the
simultaneous use of Tx control of RTSN and Rx control is mutually exclusive.
However, if this is programmed, the UART performs as required.
4
CTS Enable Tx. Clear-to-Send Control.
The state of this bit determines if the CTSN input (I/O0) controls the
operation of the transmitter. If this bit is 0, CTSN has no effect on the
transmitter. If this bit is a 1, the transmitter checks the state of CTSN each
time it is ready to begin sending a character. If it is asserted (LOW), the
character is transmitted. If it is negated (HIGH), the TXD output remains in
the marking state and the transmission is delayed until CTSN goes LOW.
Changes in CTSN, while a character is being transmitted, do not affect the
transmission of that character. This feature can be used to prevent overrun of
a remote receiver.
Please see the CTS description in Section 7.4.6 “Transmitter” for a
description of direct software control of this pin, thus giving software a direct
control of the transmitter.
3:0
Stop Bit Length Select.
This field programs the length of the stop bit appended to the transmitted
character. Stop bit lengths of ⁹⁄₁₆ bit through 2 bits can be programmed. In all
cases, the receiver only checks for a mark condition at the center of the first
stop bit position (one bit time after the last data bit, or after the parity bit if
parity is enabled). If an external 1× clock is used for the transmitter,
MR2[1] = 0 selects one stop bit and MR2[1] = 1 selects two stop bits to be
transmitted.
9397 750 13138
Product data sheet
Rev. 01 — 31 October 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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