DIRECTV Set-Top Box Information for the Installer
DIRECTV, Inc.
March 5, 2008
Version 2.2
Page 39 of 42
DTV-MD-0058
8.2 Low-Speed Electrical Performance and Characteristics
The low speed timing characteristics are defined in Table 8-1.
Table 8-1: Timing Characteristics
Parameter
Requirement
Bit Timing
104
μ
s ±7
μ
s
Total Character Interval
1.04 ms
±
8
μ
s
8.2.1 Bit Timing (Start, –D0 TO –D7, and Stop)
The STB complies with the bit timing requirements as shown in Figure 8-3.
Figure 8-3. Bit Timing Diagram
8.2.2 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.”
8.2.3 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.”
8.3 Low-Speed Input Characteristics
8.3.1 Input Signaling Characteristics (Pin 3)
The low-speed data port will comply with the input signaling characteristics shown in Table 8-2.
Total Character Interval
Start Bit
8 Data Bits
D0
D7
Idle
Stop Bit
