MC68302AG16C 产品描述及参数 - NXP（恩智浦）

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MC68302 AutoBaud Specificati

o

n - Rev.2.0

This document describes the operation, registers, and programming of the Autobaud

Microcode Package Revision 2.0. Below are the major features of Revision 2.0:

• Downloads into the MC68302 dual-port RAM.

• Requires 16 x the maximum baudrate for the sampling clock (can be internally or externally

generated).

• Supports parity determination and character length detection on reception for 7-bit characters

with parity, 8-bit characters with and without parity.

• Supports parity generation on transmission

used to implement the standard AT command set or other characters.

In order to use the AutoBaud mode, the Serial Communication Controller (SCC) is initially

programmed to BISYNC mode. The SCC receiver then synchronizes on the falling edge of the

START bit. Once a start bit is detected, each bit received is processed by the AutoBaud controller.

The AutoBaud controller measures the length of the START bit to determine the receive baudrate

and compares the length to values in a user supplied lookup table. After the baudrate is

determined, the AutoBaud controller assembles the character and compares it against two user-

defined characters. If a match is detected, the AutoBaud controller interrupts the host and returns

the determined nominal start value from the lookup table. The AutoBaud controller continues to

assemble the characters and interrupt the host until the host stops the reception process. The

package, the performance table in Appendix A of the MC68302 user’s manual can be used. The

maximum full-duplex rate for a BISYNC channel is one-tenth of the system clock rate. So a 16.67

MHz 68302 can support 115.2K AutoBaudrate with another low-speed channel (<50 kbps) and a