C
Charles Jean
- Jan 1, 1970
- 0
I've got a datasheet for a chip that takes an RS232 serial input with
a protocol of 9600,N,8,1. It indicates the voltage level at this
input is hardware-selectable to either +/- 12V(as found from a PC
serial port), and either normal or inverted TTL level(0-5V). I plan on
feeding this chip a TTL level serial stream by bit-banging it rather
than using a UART. I am familiar with the polarities and V
requirements of the "real" RS232 as shown in the example below for
ASCII 65("A"):
+15V-|------<--8 character bits---->--------------
| ___ _______________ ___
| |S | | | | |
| |T | | | | |
| |A | | | | |
+3V-|--|R-|--|--------------|--|--|--------------
| |T | | | | |INDETERMINATE
| | | | | | |VOLTAGE
0V-|--|B-|--|--------------|--|--|--------------
| |I | | | | |REGION
| |T | | | | |
-3V-|--|--|--|--------------|--|--|--------------
| | | | | | |
| | | | | | | TWO
| | | | | | | STOP
| | | | | | | BITS
____|__| |__| | | | | |__| |__|__| | | |
| 0 1 0 0 0 0 0 1 0 1 1
-15V-|------LSB------------------MSB--------------
Bit width = 1/9600 seconds = 104.2 microseconds
Can someone please educate me as to what are:
1)"normal" TTL RS232 voltage levels
2)"inverted" TTL RS232 voltage levels
TIA
Charlie
a protocol of 9600,N,8,1. It indicates the voltage level at this
input is hardware-selectable to either +/- 12V(as found from a PC
serial port), and either normal or inverted TTL level(0-5V). I plan on
feeding this chip a TTL level serial stream by bit-banging it rather
than using a UART. I am familiar with the polarities and V
requirements of the "real" RS232 as shown in the example below for
ASCII 65("A"):
+15V-|------<--8 character bits---->--------------
| ___ _______________ ___
| |S | | | | |
| |T | | | | |
| |A | | | | |
+3V-|--|R-|--|--------------|--|--|--------------
| |T | | | | |INDETERMINATE
| | | | | | |VOLTAGE
0V-|--|B-|--|--------------|--|--|--------------
| |I | | | | |REGION
| |T | | | | |
-3V-|--|--|--|--------------|--|--|--------------
| | | | | | |
| | | | | | | TWO
| | | | | | | STOP
| | | | | | | BITS
____|__| |__| | | | | |__| |__|__| | | |
| 0 1 0 0 0 0 0 1 0 1 1
-15V-|------LSB------------------MSB--------------
Bit width = 1/9600 seconds = 104.2 microseconds
Can someone please educate me as to what are:
1)"normal" TTL RS232 voltage levels
2)"inverted" TTL RS232 voltage levels
TIA
Charlie