Preliminary
UART
S3C2451 RISC MICROPROCESSOR
15-20
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
Table
15-2
Recommended value table of DIVSLOTn register
Floating point part
Num of 1’s
UDIVSLOTn
0 0
0x0000(0000_0000_0000_0000b)
0.0625 1
0x0080(0000_0000_0000_1000b)
0.125 2
0x0808(0000_1000_0000_1000b)
0.1875 3
0x0888(0000_1000_1000_1000b)
0.25 4
0x2222(0010_0010_0010_0010b)
0.3125 5
0x4924(0100_1001_0010_0100b)
0.375 6
0x4A52(0100_1010_0101_0010b)
0.4375 7
0x54AA(0101_0100_1010_1010b)
0.5 8
0x5555(0101_0101_0101_0101b)
0.5625 9
0xD555(1101_0101_0101_0101b)
0.625 10
0xD5D5(1101_0101_1101_0101b)
0.6875 11
0xDDD5(1101_1101_1101_0101b)
0.75 12
0xDDDD(1101_1101_1101_1101b)
0.8125 13
0xDFDD(1101_1111_1101_1101b)
0.875 14
0xDFDF(1101_1111_1101_1111b)
0.9375 15
0xFFDF(1111_1111_1101_1111b)
Baud-Rate Error Tolerance
UART Frame error should be less than 1.87%(3/160).
tUPCLK = (U 1) x 16 x 1Frame / PCLK tUPCLK: Real UART Clock
tEXTUARTCLK = 1Frame / baud-rate tEXTUARTCLK: Ideal UART Clock
UART error = (tUPCLK – tEXTUARTCLK) / tEXTUARTCLK x 100%
NOTE:
1Frame = start bit + data bit + parity bit + stop bit.
Error Tolerance is calculated from the timing of reading stop bit at Ideal UART clock vs Real UART clock.
From the Ideal UART clock reading stop bit timing
±
3 clock period of 16 times the baud-rate are allowed.
UART Clock and PCLK Relation
here is a constraint on the ratio of clock frequencies for PCLK to UARTCLK.
The frequency of UARTCLK must be no more than 5.5/3 times faster than the frequency of PCLK :
F
UARTCLK
<= 5.5/3 X F
PCLK
F
UARTCLK
= baudrate x 16
This allows sufficient time to write the received data to the receive FIFO