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DIRECTV Set-top box information for the installer
DIRECTV Proprietary November 17, 2005
Version 1.1.a Page 10 of 49 DTV-MD-0058
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.
Table 4: Timing Characteristics
Parameter Requirement
Bit Timing
104 µs ±7 µs
Total Character Interval
1.04 ms ± 8 µs
3.4 Bit Timing (Start, –D0 TO –D7, and Stop)
The STB complies with the bit timing requirements as shown in
Figure 3.
Figure 3. Bit Timing Diagram
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.”
Total Character Interval
Start Bit
8 Data Bits
D0 D7 Idle
Stop Bit