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Serial Communication Modules
MOTOROLA
MPC801 USER’S MANUAL
16-5
16
ICTS—Ignore CTS
When it is high, this bit forces the CTS pin to be asserted, thus effectively ignoring the
external pin. While in this mode, the CTS pin can be used as a general-purpose input.
0 = Transmit only while the CTS pin is asserted.
1 = Ignore the CTS pin.
CTSS—CTS Status
This bit indicates the current status of the CTS pin. A snapshot of the pin is taken before this
bit is presented to the data bus. When the ICTS pin is high, this bit can be used as a
general-purpose input.
0 = CTS pin is low.
1 = CTS pin is high.
CTSD—CTS Delta
When it is high, this bit indicates that the CTS pin has been changed. It generates a
maskable interrupt. The current status of the CTS pin can be found on the CTSS bit. The
CTS interrupt is cleared by writing a zero to this bit.
0 = CTS pin has not been changed since it was last cleared.
1 = CTS pin has been changed.
TX DATA—Transmit Data
These bits are the parallel transmit data inputs. When in 7-bit mode, Bit 8 is ignored. When
in 8-bit mode, all bits are used. Data is transmitted beginning with the least-significant bit. A
new character is transmitted when these bits are written.
16.2.1.2 THE RECEIVER.
parallel character. It operates in two modes—16
START bit, qualifies it, then samples the succeeding DATA bits at the bit’s center. Jitter
tolerance and noise immunity are provided by sampling at a 16
technique to clean up the samples. In 1
×
mode, the RXD bit is sampled on each rising edge
of the bit clock. Once the START bit has been found, the DATA, PARITY, and STOP bits
are shifted in.
The receiver accepts a serial datastream and converts it into a
×
and 1
×
. In 16
×
mode, it searches for a
×
rate and using a voting
If parity is enabled, it is checked and its status is reported in the receiver register. Similarly,
frame errors and breaks are checked and reported. When a new character is ready to be
read by the core, the RTS pin is asserted and an interrupt is posted (if enabled). When the
receiver register is read as a 16-bit word, the complete FIFO status, the four status bits, and
the received character byte are read by the core. The RTS pin can be configured as an
output that indicates the receiver is ready for data or it can be directly controlled by the
software.