A.

1. BUS-65112 uses a 12 MHZ clock, while BUS-65142 uses a 16 MHZ clock.
   
   
2. For a Transmit (RT-to-BC transfer) message: for BUS-65112, R/W* is low, except hat it pulses high during the transfer cycle period defined by DTREQ* being high. For BUS-65142, R/W* is low for the command word transfer, then goes high and stays high (it doesn't pulse).
   
   
3. The maximum DTREQ*-to-DTGRT* time is 1.5 µs for BUS-65112, and 2.1 µs for BUS-65142.

Q. What are the BUS-65143’s power consumption and dissipation?

A. For BUS-65143 (+5V/-12V power), the maximum current drain is:

• For +5V: 115 mA max
  
  
• For -12V: At idle (non-transmitting): 70 mA max; at 50% transmit duty cycle: 185 mA max; at 100% transmit duty cycle: 305 mA max.
  For the BUS-65143 power dissipation, assuming a total external dissipation of 1.4 watts {in the isolation transformer (140 mW), coupling transformer (80 mW), isolation resistors (450 mW each) and termination resistors (150 mW each)} when transmitting:
  
  
• At idle: 1.415 watts max
  
  
• At 50% duty cycle: 2.125 watts max
  

Q. Is there a recommended way of decoupling for the BU-61705 Simple System RT? Any particular values and number of capacitors should be used?

A. We recommend a 10 µF tantalum capacitor in parallel with a 0.1 µF ceramic capacitor for each of the two transceiver [VCC-CH. A(B)] pins (72 and 20), and a 0.1 µF ceramic capacitor on Vcc-LOGIC, pin 37.