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(3) Send out one block data (Transmit – the data more than two characters)
Step 1:
Enable TXC signal, and the bit 0 of the address of offset+4 just sets "1".
Step 2:
Send out the data. (Write all data to the offset+0 of the current COM port address)
Step 3:
Wait for the buffer' s data empty. Check transmitter holding register (THRE, bit 5 of the address of
offset+5), and transmitter shift register (TSRE, bit 6 of the address of offset+5) are all sets must be
"0".
Step 4:
Disabled TXC signal, and the bit 0 of the address of offset+4 sets "0"
(4) Receive data
The RS-485' s operation of receiving data is in the same of the RS-232' s.
(5) Basic Language Example
a.) Initial 86C450 UART
10
OPEN "COM1:9600,m,8,1"AS #1 LEN=1
20
REM Reset DTR
30
OUT &H3FC, (INP(%H3FC) AND &HFA)
40
RETURN
b.) Send out one character to COM1
10
REM Enable transmitter by setting DTR ON
20
OUT &H3FC, (INP(&H3FC) OR &H01)
30
REM Send out one character
40
PRINT #1, OUTCHR$
50
REM Check transmitter holding register and shift register
60
IF ((INP(&H3FD) AND &H60) >0) THEN 60
70
REM Disable transmitter by resetting DTR
80
OUT &H3FC, (INP(&H3FC) AND &HEF)
90
RETURN
c.) Receive one character from COM1
10
REM Check COM1: receiver buffer
20
IF LOF(1)<256 THEN 70
30
REM Receiver buffer is empty
40
INPSTR$"
50
RETURN
60
REM Read one character from COM1: buffer
70
INPSTR$=INPUT$(1,#1)
80
RETURN
AR-B1474 User¡ ¦ s Guide
9-3
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