Rainbow Electronics CAN интерфейс - Manual (Page 20)

BOSCH
ROBERT BOSCH GmbH, Postfach 50, D-7000 Stuttgart 1
Sep. 1991
Part A - page 18
OVERLOAD FLAG
consists of six ’dominant’ bits. The overall form corresponds to that of the ACTIVE
ERROR FLAG.
The OVERLOAD FLAG’s form destroys the fixed form of the INTERMISSION field. As
a consequence, all other stations also detect an OVERLOAD condition and on their
part start transmission of an OVERLOAD FLAG. (In case that there is a ’dominant’ bit
detected during the 3rd bit of INTERMISSION locally at some node, the other nodes
will not interpret the OVERLOAD FLAG correctly, but interpret the first of these six
’dominant’ bits as START OF FRAME. The sixth ’dominant’ bit violates the rule of bit
stuffing causing an error condition).
OVERLOAD DELIMITER
consists of eight ’recessive’ bits.
The OVERLOAD DELIMITER is of the same form as the ERROR DELIMITER. After
transmission of an OVERLOAD FLAG the station monitors the bus until it detects a
transition from a ’dominant’ to a ’recessive’ bit. At this point of time every bus station
has finished sending its OVERLOAD FLAG and all stations start transmission of seven
more ’recessive’ bits in coincidence.
3.1.5 INTERFRAME SPACING
DATA FRAMEs and REMOTE FRAMEs are separated from preceding frames
whatever type they are (DATA FRAME, REMOTE FRAME, ERROR FRAME,
OVERLOAD FRAME) by a bit field called INTERFRAME SPACE. In contrast,
OVERLOAD FRAMEs and ERROR FRAMEs are not preceded by an INTERFRAME
SPACE and multiple OVERLOAD FRAMEs are not separated by an INTERFRAME
SPACE.
INTERFRAME SPACE
contains the bit fields INTERMISSION and BUS IDLE and, for ’error passive’ stations,
which have been TRANSMITTER of the previous message, SUSPEND
TRANSMISSION.
Overload Frame