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Serial Channel registers
252
NS7520 Hardware Reference, Rev. D 03/2006
Max baudrates with different clock sources
Max baud rates for the serial port depend on the clock source you are using.
With the 18.432MHz crystal using XTALE as the clock source:
FXTALE = xtal/5 = 18.432MHz/5 = 3.6864MHz
This does not change with speed grade.
16X
Fbrg = FXTALE/[2 * 16 * (N+1)]
115200 = 3686400/2*16*(N+1) or
2*16*(N+1) = 3686400/115200 or
2*16*(N+1) = 32 or
N = 32/32-1 = 0
Max baudrate @ 16X = 115.2K
D10:00 R/W NREG 0 N register
The N register value is determined by the
following equations. F
BRG
must be adjusted
according to the TMODE and TDCR/RDCR
settings. For a 16x setting, for example, F
BRG
is 16 times the desired baud rate.
F
BRG
= F
XTALE
/[2*(N+1)
Using a CLKMUX setting of 00
F
BRG
= F
SYSCLK
/[2*(N+1)
Using a CLKMUX setting of 01
F
BRG
= F
OUT1
/[2*(N+1)
Using a CLKMUX setting of 10
F
BRG
= F
OUT2
/[2*(N+1)
Using a CLKMUX setting of 11
The maximum value for F
OUT1
and F
OUT2
is
F
SYSCLK
/4.
See Table 91: "Bit rate examples" on page
254 for sample bit rates.
Bits Access Mnemonic Reset Description
Table 90: Serial Channel Bit-Rate register bit definition