Rainbow Electronics DS89C450 - Manual (Page 10)

DS89C430/DS89C440/DS89C450 Ultra-High-Speed Flash Microcontrollers
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Figure 4. Serial Port Timing
t
XLXL
t
XHDV t
XHDX
t
XHQX
t
QVXH
TRANSMIT
RECEIVE
ALE
WRITE TO SBUF
PSEN
RXD DATA OUT
TXD CLOCK
TXD CLOCK
R1
TI
WRITE TO SCON
TO CLEAR RI
RXD DATA IN
D0 DI D3 D4 D2 D5 D6 D7
D7 D6 D5 D4 D3 D2 DI D0
RXD DATA IN
TXD CLOCK
R
E
C
E
IV
E
T
R
A
N
S
M
IT
D0 DI D6 D7
WRITE TO SCON
TO CLEAR RI
R1
D0 DI D6 D7
1/(XTAL FREQ/12)
ALE
PSEN
WRITE TO SBUF
RXD DATA OUT
TXD CLOCK
TI
TXD CLOCK
SERIAL PORT (SYNCHRONOUS MODE)
SM2 = 0 TDX CLOCK = XTAL FREQ/12
SERIAL PORT (SYNCHRONOUS MODE)
SM2 = 1 TDX CLOCK = XTAL FREQ/4