258
MC97F60128
ABOV Semiconductor Co., Ltd.
11.13.12
USI0/1 UART Parity Generator
The parity generator calculates the parity bit for the serial frame data to be sent. When parity bit is enabled
(USInPM1=1), the transmitter control logic inserts the parity bit between the MSB and the first stop bit of the frame to
be sent.
11.13.13
UART Disabling Transmitter
Disabling the transmitter by clearing the TXEn bit will not become effective until ongoing transmission is completed.
When the Transmitter is disabled, the TXDn pin can be used as a normal general purpose I/O (GPIO).
11.13.14
USI0/1 UART Receiver
The UART receiver is enabled by setting the RXEn bit in the USInCR2 register. When the receiver is enabled, the
RXDn pin should be set to RXDn function for the serial input pin of UART by P3FSRL[5:4]/P5FSRH[6:5]. The baud-
rate, mode of operation and frame format must be set before serial reception. In synchronous or SPI operation mode
the SCKn pin is used as transfer clock, so it should be selected to do SCKn function by P3FSRL[1:0]/P5FSRH[2:1]. In
SPI operation mode the SSn input pin in slave mode or can be configured as SSn output pin in master mode. This can
be done by setting USInSSEN bit in USnCR3 register.
11.13.15
USI0/1 UART Receiving Rx data
When UART is in synchronous or asynchronous operation mode, the receiver starts data reception when it detects a
valid start bit (LOW) on RXDn pin. Each bit after start bit is sampled at pre-defined baud-rate (asynchronous) or
sampling edge of SCKn (synchronous) and shifted into the receive shift register until the first stop bit of a frame is
received. Even if there’s 2
nd
stop bit in the frame, the 2
nd
stop bit is ignored by the receiver.
That is, receiving the first
stop bit means that a complete serial frame is present in the receiver shift register and contents of the shift register are
to be moved into the receive buffer. The receive buffer is read by reading the USInDR register.
If 9-bit characters are used (USInS
[2:0] = “111”), the ninth bit is stored in the USInRX8 bit position in the USInCR3
register. The 9
th
bit must be read from the USInRX8 bit before reading the low 8 bits from the USInDR register.
Likewise, the error flags FEn, DORn, PEn must be read before reading the data from USInDR register. It
’s because
the error flags are stored in the same FIFO position of the receive buffer.
Содержание MC97F60128
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Страница 19: ...19 MC97F60128 ABOV Semiconductor Co Ltd Figure 4 3 80 Pin LQFP 1414 Package...
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