MC68HC908GZ8 Datasheet, PDF (245/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Enhanced Serial Communications Interface (ESCI) Module
I/O Registers
LINT — LIN Break Symbol Transmit Enable
This read/write bit selects the enhanced ESCI features for master nodes in the
local interconnect network (LIN) protocol (version 1.2) as shown in Table 19-6.
Reset clears LINT.
Table 19-6. ESCI LIN Master Node Control Bits
LINT
0
1
1
M
Functionality
X Normal ESCI functionality
0 13-bit generation enabled for LIN transmitter
1 14-bit generation enabled for LIN transmitter
NOTE:
LIN master nodes require significantly tighter timing tolerances than slave nodes.
Be sure to consult the current LIN specification to ensure that timing requirements
are met properly. Generally, these timing tolerances require crystals or oscillators
to be used, rather than internal clocking circuits.
LINR — LIN Break Symbol Receiver Bits
This read/write bit selects the enhanced ESCI features for slave nodes in the
local interconnect network (LIN) protocol as shown in Table 19-7. Reset clears
LINR.
Table 19-7. ESCI LIN Slave Node Control Bits
LINR
0
1
1
M
Functionality
X Normal ESCI functionality
0 11-bit break detect enabled for LIN receiver
1 12-bit break detect enabled for LIN receiver
In LIN (version 1.2) systems, the master node transmits a break character which
will appear as 11.05–14.95 dominant bits to the slave node. A data character of
0x00 sent from the master might appear as 7.65–10.35 dominant bit times. This
is due to the oscillator tolerance requirement that the slave node must be within
±15% of the master node's oscillator. Since a slave node cannot know if it is
running faster or slower than the master node (prior to synchronization), the
LINR bit allows the slave node to differentiate between a 0x00 character of
10.35 bits and a break character of 11.05 bits. The break symbol length must be
verified in software in any case, but the LINR bit serves as a filter, preventing
false detections of break characters that are really 0x00 data characters.
MC68HC908GZ8
MOTOROLA
Enhanced Serial Communications Interface (ESCI) Module
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Data Sheet
245