Jameco Electronics Rabbit 3000 - Manual (Page 177)

168 Rabbit 3000 Microprocessor
Table 12-8. Data Register All Ports
Serial Port x Data Register (SADR) (Address = 0xC0)
(SBDR) (Address = 0xD0)
(SCDR) (Address = 0xE0)
(SDDR) (Address = 0xF0)
(SEDR) (Address = 0xC8)
(SFDR) (Address = 0xD8)
Bit(s) Value Description
7:0
Read Returns the contents of the receive buffer.
Write Loads the transmit buffer with a data byte for transmission.
Table 12-9. Address Register All Ports
Serial Port x Address Register (SAAR) (Address = 0xC1)
(SBAR) (Address = 0xD1)
(SCAR) (Address = 0xE1)
(SDAR) (Address = 0xF1)
(SEAR) (Address = 0xC9)
(SFAR) (Address = 0xD9)
Bit(s) Value Description
7:0
Read
Returns the contents of the receive buffer. In Clocked Serial mode reading the
data from this register automatically causes the receiver to start a byte receive
operation (the current contents of the receive buffer are read first), eliminating
the need for software to issue the Start Receive command.
Write
Loads the transmit buffer with an address byte, marked with a “zero” address bit,
for transmission. In HDLC mode, the last byte of a frame must be written to this
register to enable subsequent CRC and closing Flag transmission. In Clocked
Serial mode writing the data to this register causes the transmitter to start a byte
transmit operation, eliminating the need for the software to issue the Start
Transmit command.