Artesyn Embedded Technology ATCA-7370, Инструкция по установке и эксплуатации

Страница: 147 / 252

Maps and Registers
ATCA-7370/ATCA-7370-S Installation and Use (6806800P54G)
147
6.2.5.10 Scratch Register (SCR)
This 8-bit read/write register has no effect on the UART. It is intended as a scratchpad register
for use by the programmer.
6.2.6 Programmable Baud Rate Generator
The UART contains a programmable Baud Rate Generator that is capable of taking the
UART_CLK input and dividing it by any divisor from 1 to (2 16 -1). The output frequency of the
Baud Rate Generator is 16 times the baud rate. Two 8-bit latches store the divisor in a 16-bit
binary format. These Divisor Latches must be loaded during initialization to ensure proper
operation of the Baud Rate Generator. If both Divisor Latches are loaded with 0, the 16X output
clock is stopped. Upon loading either of the Divisor latches, a 16-bit baud counter is
immediately loaded. This prevents long counts on initial load. Access to the Divisor latch can be
done with a word write.
The UART_CLK is the CLK_UART (48MHz) input divided by the pre-divider set by the Super IO
Configuration Register (Offset 0x29).
The baud rate of the data shifted in/out of the UART is given by:
Baud Rate = UART_CLK / (16X Divisor)
For example, if the pre-divider is 26 the UART_CLK is 1.8461538MHz. When the divisor is 12,
the baud rate is 9600.
Table 6-39 Scratch Register (SCR)
LPC IO Address: Base + 7
Bit Description Default Access
7:0 Scratch Register (SCR)
The scratch register is an 8 bit register that is
intended for the programmer's use as a
scratch pad in the sense that it temporarily
holds the programmer's data without
affecting any other ACE operation. Undefined LPC: r/w