Yamaha CRX-E150 Service Manual page 54

CRX-E150
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Microprocessor peripheral circuit
Transmission
Reception
CPU
Description of main system operation
1) POWER ON/OFF processing [(1) to (4)]
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CRX
• The power cord of each unit is connected to the AC outlet in series and switched on and off
through the CRX relay.
• Turning off the CRX power switch will turn off the power to other units (primary connection) but
turning off the power switch of any other unit will turn off the secondary connection of each unit
only (i.e., the microprocessor remains on).
• Each unit has a backup function to save the secondary connection status when unplugged
(taking use of a unit alone into consideration)
• The indicators of units are turned on after a dimmer level signal is fed from CRX so that they
light up simultaneously when the CRX power switch is turned on. However, as the indicator of a
unit does not light up when the unit is used alone in this setting, the indicator is forced to turn on
when 2 seconds have elapsed without a dimmer level signal being fed (and the power for the
backup function is turned on).
• Make sure that the power off processing of each unit has been completed before turning off the
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power by using the CRX relay.
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System cable
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Description of data transmission and reception
1 Although there is only 1 bus line, prepare special ports
for data transmission and reception at each CPU.
2 The bus data consists of a header and data (8 bits).
CPU receives and transmits at a 0.5mS or less timer
interruption.
3 The header is used to identify the model and to
prevent butting by changing the length for each unit.
4 At each CPU, data transmission and reception are
carried out independently. Before transmitting the data,
be sure to check the reception status. If the data is being
received, wait until the data has been received and then
transmit the data.
5 When the data transmission is completed, each CPU
also checks the received data. If the header of the
received data does not agree with its own head, the data
may have been overlapped by that of the other model. In
such case, stop the data transmission and restart it after
confirming that the the data transmission of other model
has been completed. This means that the unit with a
longer header has a higher priority.
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