Digi NS7520B-1-C36 Hardware Reference Manual page 260

S e r i a l C h a n n e l r e g i s t e r s
FXTALE = xtal/5 = 18.432MHz/5 = 3.6864MHz
This does not change with speed grade.
16X
8X
With the 18.432MHz crystal using SYSCLK as the clock source:
Max. baudrate depends on speed grade. Max. programmable baudrate = SYSCLK/32;
max recommended baudrate is 922K.
16X @ 55.296MHz
16X @ 46.08MHz
2 4 8
Fbrg = FXTALE/[2 * 16 * (N+1)]
115200 = 3686400/2*16*(N+1)
2*16*(N+1) = 3686400/115200
2*16*(N+1) = 32
N = 32/32-1 = 0
Max baudrate @ 16X = 115.2K
Fbrg = FXTALE/[2 * 8 * (N+1)]
230400 = 3686400/2*8*(N+1)
2*8*(N+1) = 3686400/230400
2*8*(N+1) = 16
N = 16/16-1 = 0
Max baudrate @ 8X = 230.4K
Fbrg = SYSCLK/[2 * 16 * (N+1)]
1728000 = 55296000/2*16*(N+1)
2*16*(N+1) = 55296000/1728000
2*16*(N+1) = 32
N = 32/32-1 = 0
Max programmable baudrate = 1,728K
Fbrg = SYSCLK/[2 * 16 * (N+1)]
1440000 = 46080000/2*16*(N+1)
2*16*(N+1) = 46080000/1440000
2*16*(N+1) = 32
N = 32/32-1 = 0
N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v G 9 / 2 0 0 7
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