Slave LIN Interface Controller (SLIC) Module
MC68HC908QL4 MC68HC908QL3 MC68HC908QL2 Data Sheet, Rev. 4
166
Freescale Semiconductor
Figure 14-19. SLCBT Value Calculation Example 2
Figure 14-20. SLCBT Value Calculation Example 3
Figure 14-21. SLCBT Value Calculation Example 4
This resolution affects the sampling accuracy of the SLIC module on receiving bytes, but only as far as
locating the sample point of each bit within a given byte. The best sample point of the bit may be off by
as much as one SLIC clock period from the exact center of the bit, if the proper SLCBT value for the
desired bit rate is an odd number of SLIC clock periods.
4 CGMXCLK Period
42.67 SLIC Clock Periods
1 Bit
1 SLIC Clock Period
1 SLIC Clock Period
406.90 ns
X
=
1 SLIC Clock Period
=
406.90 ns
1 Second
57,600 Bits
=
17.36111 ms
1 Bit
9,830,400 CGMXCLK Periods
1 Second
X
17.36111 ms
1 Bit
Desired Bit Rate: 57,600 bps
External Crystal Frequency: 9.8304 MHz
Therefore, the closest SLCBT value would be 42 SLIC clocks (SLCBT = 0x002A).
4 CGMXCLK Period
128 SLIC Clock Periods
1 Bit
1 SLIC Clock Period
1 SLIC Clock Period
500 ns
X
=
1 SLIC Clock Period
=
500 ns
1 Second
15,625 Bits
=
64 ms
1 Bit
8,000,000 CGMXCLK Periods
1 Second
X
64 ms
1 Bit
Desired Bit Rate: 15,625 bps
External Crystal Frequency: 8.000 MHz
Therefore, the closest SLCBT value would be 128 SLIC clocks (SLCBT = 0x0080).
4 CGMXCLK Period
208.008 SLIC Clock Periods
1 Bit
1 SLIC Clock Period
1 SLIC Clock Period
500 ns
X
=
1 SLIC Clock Period
=
500 ns
1 Second
9,615 Bits
=
104.004 ms
1 Bit
8,000,000 CGMXCLK Periods
1 Second
X
104.004 ms
1 Bit
Desired Bit Rate: 9.615 bps
External Crystal Frequency: 8.000 MHz
Therefore, the closest SLCBT value would be 42 SLIC clocks (SLCBT = 0x00D0).