Rabbit Rabbit 4000, User Manual

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156 Rabbit 4000 Microprocessor User’s Manual
Serial Port x Status Register (SESR) (Address = 0x00CB)
(Asynchronous Mode Only) (SFSR) (Address = 0x00DB)
Bit(s) Value Description
7 0 The receive data register is empty
1
There is a byte in the receive buffer. The serial port will request an interrupt
while this bit is set. The interrupt is cleared when the receive buffer is empty.
6 0 The byte in the receive buffer is data, received with a valid stop bit.
1
The byte in the receive buffer is an address, or a byte with a framing error. If an
address bit is not expected, and the data in the buffer is all zeros, this is a break.
5 0 The receive buffer was not overrun.
1 The receive buffer was overrun. This bit is cleared by reading the receive buffer.
4 0 The byte in the receive buffer has no parity error (or was not checked for parity).
1 The byte in the receive buffer had a parity error.
3 0 The transmit buffer is empty.
1
The transmit buffer is not empty. The serial port will request an interrupt when
the transmitter takes a byte from the transmit buffer. Transmit interrupts are
cleared when the transmit buffer is written, or any value (which will be ignored)
is written to this register.
2 0 The transmitter is idle.
1
The transmitter is sending a byte. An interrupt is generated when the transmitter
clears this bit, which occurs only if the transmitter is ready to start sending
another byte and the transmit buffer is empty.
1:0 00 These bits are always zero in async mode.