MPC823 datasheet(14/74 Pages) MOTOROLA

14 / 74 page

Communication Processor Module

16-392

MPC823 REFERENCE MANUAL

MOTOROLA

• MAX_IDL—Once a character of data is received on the line, the SMCx UART controller

starts counting any idle characters received. If a MAX_IDL number of idle characters is

received before the next data character, an idle timeout occurs and the buffer closes.

This, in turn, produces an interrupt request to the core to receive the data from the

buffer. MAX_IDL provides a convenient way to demarcate frames in SMCx UART

mode. But if you do not want to use MAX_IDL, you must program MAX_IDL to 0x0000

and the buffer will never close, regardless of the number of idle characters received.

The number of bits in an idle character is calculated as follows—1 + character data

length (5 to 14) + 1 (if parity bit is used) + number of stop bits (1 or 2). For example, for

a character data length of 8, no parity, and 1 stop bit, the idle character length is 10 bits.

• IDLC—This value is used by the RISC microcontroller to store the current idle counter

value in the MAX_IDL timeout process. IDLC is a down-counter that you do not need to

initialize or access.

• BRKLN—This value is used to store the length of the last break character received and

is the bit length of that character. For example, if the receive pin is low for 257 bit times,

BRKLN shows the value 0x0101 and its accuracy comes within one character unit of

bits. For 8 data bits, no parity, 1 stop bit, and 1 start bit, BRKLN is accurate within 10

bits.

• BRKEC—This counter counts the number of break conditions that occur on the line.

One break condition can last for hundreds of bit times, yet this counter is only

incremented once during that period.

• BRKCR—This value indicates when the SMCx UART controller sends a break

character sequence after a STOP TRANSMIT command is issued. The number of

break characters sent by the SMCx UART controller is determined by the value in

BRKCR. For 8 data bits, no parity, 1 stop bit, and 1 start bit, each break character is 10

bits long and consists of all zeros.

• R_MASK—This value is a temporary bit mask used internally by the SMCx UART

controller.

16.11.6.5 PROGRAMMING THE SMCx UART CONTROLLER. The SMCx UART

controller’s data structure supports multibuffer operation and allows you to transmit break

and preamble sequences. Overrun, parity, and framing errors are reported via the buffer

descriptors. In its simplest form, the SMCx UART controller functions in a character-oriented

environment. Each character is transmitted with the stop bits and parity that you configure.

Characters are received into separate 1-byte buffers. A maskable interrupt can be

generated when each buffer is filled.

Many applications may want to take advantage of the message-oriented capabilities that the

SMCx UART controller supports through linked buffers for reception or transmission. You

can handle data in a message-oriented environment and work on entire messages rather

than on a character-by-character basis. A message can span several linked buffers and

each one can be transmitted and received as a linked list of buffers without any intervention

from the core, which makes it easy to program and saves processor overhead. In a

message-oriented environment, the idle sequence is used as the message delimiter. The

transmitter can generate an idle sequence before starting a new message and the receiver

can close a buffer when an idle sequence is found.

MPC823 датащи(PDF) 14 Page - Motorola, Inc

MPC823 датащи(HTML) 14 Page - Motorola, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

датащи скачать

ссылки URL