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DIRECTV Set-top box information for the installer
The majority of STBs have a default baud data rate of 9600. The data format is 1 start bit, 8 data
bits, no parity, 1 stop bit, and no handshaking.
3.3 Low-Speed Electrical Performance and Characteristics
The low speed timing characteristics are defined in Table 4.
Bit Timing
Total Character Interval
3.4 Bit Timing (Start, –D0 TO –D7, and Stop)
The STB complies with the bit timing requirements as shown in
Figure 3.
Start Bit
D0
3.5 Idle Interval, General
The general idle interval is a minimum of zero (0) msec. The maximum idle interval will be
determined by the rate of transmitted data and internal STB processes when the port is "opened,"
or is determined by the service command parser when the port is "closed."
3.6 Idle Interval for Non-Empty STB Buffer
The idle interval will not exceed 30 ms as long as at least one byte exists in the STB receive
buffer, given that the port is "opened."
DIRECTV Proprietary
Version 1.1.a
Table 4: Timing Characteristics
Parameter
Total Character Interval
8 Data Bits
Figure 3. Bit Timing Diagram
Page 10 of 49
Requirement
104 µs ±7 µs
1.04 ms ± 8 µs
Stop Bit
D7
Idle
November 17, 2005
DTV-MD-0058
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