Microsemi SmartFusion2 - Figure 182 Example with Fractional Baud Rate of 4.5; Figure 183 • Example with Fractional Baud Rate of 2 and 3;64

MMUART Peripherals
UG0331 User Guide Revision 15.0 477
The following figure describes the timing for a fractional baud rate value of 4.5. Exact averaging is
accomplished in one Tbit (bit time) cycle.
Figure 182 • Example with Fractional Baud Rate of 4.5
Notes:
• Lowest Common Denominator Value of 32 requires two Tbit times to complete the time modulation
fractional baud rate. Lowest Common Denominator Value of 64 requires four Tbit times to complete
the time averaged fractional baud rate. Thus, depending on the fraction chosen, the Tbit time may or
may not be constant for 2 or 4 Tbit times max, but the time averaged Tbit time will be correct.
• Do not use the integer divisor value of 1 when in Fractional mode.
The following figure shows the timing for a fractional baud rate value of 2 and 3/64
th
. Exact averaging is
accomplished in four Tbit cycles due to 64
th
granularity.
Figure 183 • Example with Fractional Baud Rate of 2 and 3/64
th
13.2.4.1.2 Input Clock-Synchronous-Slave Mode
MMUART supports a synchronous Master and Slave mode. In the synchronous Slave mode, the
MMUART accepts an input clock that is synchronized to the data. The asynchronous state machine is
harnessed to self-synchronize the start bit to a clock edge. With this circuit, the input clock can be
Bit Rate Modulation with Tbit Times
BR = 4 = 64 CCC per count
BR = 5 = 16x5 = 80 CCC per count
Integer + 1 Tbit
Integer Tbit
Integer Tbit
Fractional Tbit
4 and 32/64
th
= 4.5
Shown is Tbit modulation of 4 and 5
integer divisor value bit rates to achieve
an average bit rate of 4 and 1/2 or 4.5.
BR = DMR+DLR
BR = DMR+DLR+1
0
00
1
11
2
2
23
3
4
4
5
5
6
6
7
0
1
2
3
45
6
7
3
4
56
7
7
0
0
1
1
2
2
3
3
4
4
5
5
5
6
6
7
7
0
0
1
1
2
23
3
4
4
4
5
5
6
6
7
7
012 3456701234567
012 3456701234567012345 670123456 7
01234
5
6
7
01234 56 7
1
234
5
6
70
1
2
3
4567 12 4 45
6
03 6
7
0123
7
0 1234 56701 2 4567
1
24
45
6
0
3567
0
1
2
37
5
3
0
0011
2
233
3
44556677
Bit Rate Modulation with Tbit Times
BR = 3 = 16x3 = 48 CCC per count
BR = 2 = 32 CCC per count
Integer + 1 Tbit
Integer Tbit
Integer Tbit
Integer Tbit
Integer Tbit
Fractional Tbit
Average BR = 2
Average BR = (2 x 61 + 3 x 3)/64 = 1 31/64 = 2 3/64
Fractional Tbit
Fractional Tbit Fractional Tbit
BR = DMR+DLR
BR = DMR+DLR+1
th