I/O modules • 243
RS232C interface 750-650
Modular I/O System
ETHERNET TCP/IP
An example:
The module is initialized.
- The initialization bit in the control byte is set.
Output byte 0
Control byte
Output byte 2
Output byte 1
0x00
0000.0100
0x00
0x00
- After the initialization has been executed, the status byte will give back
000.0100.
Input
byte 0
Status byte
Input
Byte 2
Input
byte 1
XX
0XXX.X0XX
XX
XX
Module is still being reset.
XX
0XXX.X1XX
XX
XX
Initialization completed.
Sending of the data string "Hello” in ASCII code:
-The first 3 characters and the buffer length of 3 are transmitted.
Output
byte 0
Control byte
Output
byte 2
Output
byte 1
‘H’ (0 x 48)
0011.0000
‘l’ (0 x 6C)
‘e’ (0 x 60)
Entering data to module
-The transmission request bit (TR) is inverted.
Output
byte 0
Control byte
Output
byte 2
Output
byte 1
‘H’
0011.0001
‘l’
‘e’
Send Data
-As soon as TR=TA, the rest of the data can be sent.
Input
byte 0
Status byte
Input
Byte 2
Input
byte 1
XX
0XXX.XXX0
XX
XX
The data is still being trans-
ferred.
XX
0XXX.XXX1
XX
XX
Data transfer completed.
-The last 2 characters and the buffer length of 2 are transmitted.
Output byte 0
Control byte
Output byte 2
Output byte 1
‘l’
0010.0001
XX
‘o’ (0 x 6F)
-The transmission request bit (TR) is inverted.
Output byte 0
Control byte
Output byte 2
Output byte 1
‘l’
0010.0000
XX
‘o’
- As soon as TA = TR, the data has been transferred to the output buffer.