User`s guide

LZ87010 Advance User’s Guide UARTs
1/15/03 10-3
10.1.2 Transmit Operation
In Modes 1-3, writing to the SBUF or SBUF1 register causes the data written to be sent
out the TXD0 or TXD1 pin in the same serial format as described for the received data. For
formats with nine-bit data (Modes 2 and 3), the ninth bit comes from the SCON.TB8 or
SCON1.TB8 bit field. See Figure 10-3.
In Mode 0, writing to the SBUF or SBUF1 register causes the data to be sent out the RXD0
or RXD1 pin (which is used for both sending and receiving data in this mode). The serial
clock is provided on TXD0 or TXD1. The receiving device should sample the serial data on
the rising edge of the serial clock. See Figure 10-4.
Because the transmit section will not drive the bus unless software writes to SBUF or
SBUF1 register, the transmit section does not require an enable/disable bit to allow the pin
to be shared with other functions.
Figure 10-2. Receive Operation, Mode 0
LZ87010-94
SCON.REN
SCON.RI
OLD RI
NEW RI
See NOTE 1
See NOTE 2
NOTES:
1. Done = 1 If shifting is complete AND (RI_IN = 0)
2. Serial data is 8 bits in mode 0 ( no START bit, 8 data bits, no STOP bit)
SCON.SMOD[1:0]
SBUF
INTERNAL TO
THE LZ87010
EXTERNAL TO
THE LZ87010
DONE EN
CLK
MODE
RI_IN
RCV
RECEIVE
CONTROL
IN
WE
SAMPLE
TO
INTERRUPT
CONTROLLER
16X
SERIAL
CLOCK
SHIFT
D7 D6 D5 D4 D3 D2 D1
SHIFT DIRECTION
RXD(x)
(Transmit and
Receive Data)
TXD(x)
(Serial
Clock)
D0
RECEIVE SHIFT
REGISTER
TXD(x) CLK
OUTPUT
RXD(x)
INPUT
SCON.RI
D0 D1 D2 D3 D4 D5 D6 D7
MODE 0 RECEIVE TIMING