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Jumper CJ-A or CJ-B
The jumper selection socket in A3 serves serial I/O channel
A and the jumper selection socket in B8 serves serial I/O
circuit B.
Their functions are the same for their respec
tive channels.
permit the serial I/O port RS232' levels to be wired so as
to either serve as the terminal end of a 232 line or the
computer end o f a 232 line with no special cable wiring
required off the Serial I/O board.
With pins 1, 2, 4, 5, 7 and 8 wired directly across the
jumper socket as shown in the diagram for the terminal
end, the function of the lines correspond one to one with
the names of the RS232 control lines referred to in the
8251 specifications.
The inputs and outputs are arranged as appropriate for the
SIO board to serve as the terminal end of an RS232 line.
Should it be desired for the SIO board to serve as the
computer end of a standard RS232 line, use jumpers con
nected as shown in the diagram.
reversed so that TRANSMIT DATA is now driving what is re
ceived data for the terminal and RECEIVE DATA is receiving
what is transmit data from the terminal, and similarly,
REQUEST TO SEND and CLEAR TO SEND are reversed and DATA
SET READY and DATA TERMINAL READY are reversed.
Ground and +5 volts are available on the socket for pro
viding permanent m a r k or space levels to any of the con
trol lines if CLEAR TO SEND is not driven by an external
source.
It should be wired to pin 6 to provide a constant
enable for the transmitter section of the USART.
Jumper Socket BJ
Socket BJ serves both to determine whether CARRIER DETECT
is being originated or received b y the SIO board.
also used to jumper the control lines between channel A
and channel B for applications where the control lines
are desired to be passed through and data intercepted and
The function of this jumper socket is to
SIO 2 Board Rev. 3
Users Guide
Edition 2
The 3 pairs of lines are
It is
9 - 29
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