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Jumper Location DJ, Located in Al
The jumper select socket in Al provides facilities for
originating and receiving clock signals for receive or
transmit for use in the synchronous mode of communication.
One-half of the socket controls lines for Channel A and
the other half is dedicated to Channel B.
4, and 13, 14, 15 and 16 serve the channel A jumper
functions.
The remainder of the pins have the identical
function for Channel B.
When it is desired to originate the clock signal the pins
for that channel should be jumpered straight across, as
shown in the diagram, so that the clock signal from the
SIO board is driven through converters to RS232 levels
onto the DD and DB lines.
The inputs to the data clock receive circuits are tied to
-12 volts to provide an inactive output to the OR-gate
supplying the receive clock to the USART chip.
When it is desired instead to receive the clock from the
RS232 cable, then these jumpers are removed and the RS232
lines DD and DB are jumpered to the input of the clock-
receive circuits as shown in the diagram.
When this is done, the data rate select socket for the
appropriate channel must be jumpered so that the clock
line from this jumper select socket is held at ground or
low in order to avoid interference between the onboard
clock circuit and the incoming clock from the RS232 line.
Data Rate Select Socket
The jumper socket in position Bll provides for selecting
different baud rates for both Channel A and Channel B from
the set of standard rates prodded by the SIO board.
pin numbers and baud rates are indicated in the diagram.
The clock lines for Channel A and Channel B are completely
independent and m ay be jumpered to the same rate or dif
ferent rates.
When the chip is being used in the synchronous mode, the
chip is running at a IX clock rate rather than 16 X rate
as in the asynchronous mode.
times as great for the same jumper location when used in
the synchronous mode.
Revision 1
Pins 1, 2, 3,
Thus, the baud rates are 16
The
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