MAC7200 datasheet(707/976 Pages) FREESCALE

707 / 976 page

eSCI Protocol

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

629

— HEADER (sent by the Master Node)

– SYNCH BREAK Field - Consists of (min) 13 “low” bits + (min) 1 “high” bit

– SYNCH Field - 1 byte ($55)

– IDENT Field - 1 byte with 6 IDENTIFIER bits and 2 PARITY bits

— Inframe response space - between the HEADER and the RESPONSE, the bus may go high

(recessive) for anywhere between 0 and x bits. ‘x’ may be as long as need be, as long as the

Maximum Frame timing requirement is not violated.

— RESPONSE (sent by the Master or Slave Node)

– DATA Fields (2,4 or 8 per Message Frame) - 1 byte (LSB first) per Field

– CHECKSUM Field - 1 byte (LSB first) per Field

— Interbyte space - between each DATA/CHECKSUM byte, the bus may go high (recessive) for

anywhere between 0 and x bits. ‘x’ may be as long as need be, as long as the Maximum Frame

timing requirement is not violated.

This gives us the following Message Frame timings:

•

Min. Message Frame (TFRAME_MIN)

14 bits (SYNCH BREAK) + 1 byte (SYNCH) + 1 byte (IDENT) + #DATA * 1 byte + 1 byte (CHECKSUM)

= 44 bits + #DATA_FIELDS * 10 bits

= 64 bits (2 byte DATA payload)

= 84 bits (4 byte DATA payload)

= 124 bits (8 byte DATA payload)

•

Max. Message Frame (TFRAME_MAX)

(TFRAME_MIN + 1) * 1.4

= 65 bits * 1.4 = 91 bits (2 byte DATA payload)

= 85 bits * 1.4 = 119 bits (4 byte DATA payload)

= 125 bits * 1.4 = 175 bits (8 byte DATA payload)

•

Min. HEADER (THEADER_MIN)

13 bits + 1 bits (SYNCH BREAK) + 1 byte (SYNCH) + 1 byte (IDENT)

= 34 bits

•

Max. HEADER (THEADER_MAX)

(THEADER_MIN + 1) * 1.4

= 35 bits * 1.4 = 49 bits

MAC7200 Datasheet(PDF) 707 Page - Freescale Semiconductor, Inc