STV3550B STMicroelectronics, STV3550B Datasheet - Page 124

• Manufacturer Part Number: STV3550B
• Manufacturer: STMicroelectronics

Specifications of STV3550B

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / Rohs Status: Compliant

TV chassis control
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The TimeoutNotEmpty bit of the ASC_n_Status register is ‘1’ when the input FIFO is not
empty and the time-out counter is zero.
The TimeoutIdle bit of the ASC_n_Status register is ‘1’ when the input FIFO is empty and
the time-out counter is zero.
The effect of this is that whenever the input FIFO has got something in it, the time-out
counter will decrement until something happens to the input FIFO. If nothing happens, and
the time-out counter reaches zero, the TimeoutNotEmpty bit of the ASC_n_Status register
will be set.
When the software has emptied the input FIFO, the time-out counter will reset and start
decrementing. If no more characters arrive, when the counter reaches zero the TimeoutIdle
bit of the ASC_n_Status register will be set.
Baud rate generation
Each ASC has its own dedicated 16-bit baud rate generator with 16-bit reload capability.
The baud rate generator has two possible modes of operation.
The ASC_n_BaudRate register is the dual-function baud rate generator and reload value
register. A read from this register returns the content of the counter or accumulator
(depending on the mode of operation); writing to it updates the reload register.
If the Run bit of the control register is 1, then any value written in the ASC_n_BaudRate
register is immediately copied to the counter/accumulator. However, if the Run bit is 0 when
the register is written, then the counter/accumulator will not be reloaded until the first
subsystem clock cycle after the Run bit is 1.
The baud rate generator supports two modes of operation, offering a wide range of possible
values. The mode is set via the BaudMode bit in the ASC_n_Control register. Mode 0 is a
simple counter driven by the subsystem clock whereas Mode 1 uses a loop-back
accumulator. Mode 0 is recommended for low baud rates (below 19.2 K baud), where its
error deviation is low, and Mode 1 is recommended for baud rates above 19.2 K.
Baud rates
The baud rate generator provides an internal oversampling clock at 16 times the external
baud rate. This clock only ticks if the Run bit of the ASC_n_Control register is set to 1.
Setting this bit to 0 will immediately freeze the state of the ASCs transmitter and receiver.
Mode 0
When the BaudMode bit in the ASC_n_Control register is set to 0, the baud rate and the
required reload value for a given baud rate can be determined by the following formula:
where: ASCBaudRate represents the content of the ASC_n_BaudRate reload value
register, taken as an unsigned 16-bit integer and f
The baud rate counter is clocked by the subsystem clock. It counts downwards and can be
started or stopped by the Run bit in the ASC_n_Control register. Each underflow of the timer
provides one oversampling baud rate clock pulse. The counter is reloaded with the value
stored in its 16-bit reload register each time it underflows.
BaudRate =
16 x ASCBaudRate
f
CPU
ASCBaudRate =
CPU
is the frequency of the CPU.
16 x BaudRate
f
CPU
STV3550