422TTL2495 - pg. 1/2
B&B Electronics October 1993
Four-Channel RS-422 to TTL Converter
Model 422TTL
Document No. 422TTL2495
The 422TTL unit converts RS-422 signals to TTL signals. Two channels are
used to convert from RS-422 to 0-+5 VDC TTL signals and two channels are used to
convert from 0-+5 VDC TTL signals to RS-422. A male DB25P connector is provided
for the TTL side and a DB25S female connector for the RS-422 side. This converter
supports RD, TD, RTS, and CTS.
The pins used are:
DB25P Male
DB25S Female
TTL
RS-422
Pin
Function
Pin
TD
9
(input) ............TD(A) .......................2
(output)
TD (B) .....................14
(output)
RD
14
(output).. .......RD (A)......................3
(input)
RD (B).....................16
(input)
RTS
16
(input) .... .......RTS (A)....................4
(output)
RTS (B)...................19
(output)
CTS
23
(output).. .......CTS (A)....................5
(input)
CTS (B)...................13
(input)
Pin 7 is signal ground for both connectors of the unit. The unit can work at baud rates up to 115K baud. Open
pads are provided for each line. Therefore, if you choose to, you can change the pin connectors for any of the 4 TTL
channels. Also, there are pads provided that allow you to change the pin connectors on the RS-422 side. A +12VDC (100
mA) power supply is needed for the unit. B&B Model 422PS can be used for this. The TTL outputs can sink up to 50 mA.
Signal levels are inverted by the converter. Please refer to the table below.
POLARITY
RS-422 Output
TTL Input
V (A) - V (B)
Units
high
negative
volts
low
positive
volts
RS-422 Input
TTL Output
V (A) - V (B)
Units
high
negative
volts
low
positive
volts
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