Sony KD-34XBR2 Training Manual page 40

RXD/TXD bus
Normal Operation
The individual RXD and TXD lines are active at:
•
TV power ON,
•
The end of a microprocessor program (periodic activity), and
•
When the Q box is needed.
At power ON, there is bi-directional communications between the Main Micro (IC001) on the B board and the
Digital Processor in the Q box.
After power ON in normal operation, there is periodic communications on the TXD/RXD lines initiated by IC001
that results in just an acknowledgment (RXD) pulse. Communications is also present when changes to the Q
box operation are called for, as shown in Waveform 10-1. Note that the normal output of IC001 is 5Vp-p and
the reply signal from the Q box is only 3Vp-p because of their operating B+ levels.
While the TV is operating, there is only periodic communications when required. Waveform 10-1 shows typical
Q box to Main Micro IC001 (B Bd) bi-directional communications. This waveform was taken when changing
into a DTV station (channel up command).
In the waveform sequence below, notice that the Main Micro starts the communications (ch 2) and the Q box
micro replies afterwards (ch 1). When changing into NTSC stations the Q box does not have to select a
station so there is no (ch 1) reply (acknowledgment).
Channel
1
2
Time Base = 2msec/div.
* Taken when channel changing into a DTV station. When changing to
another NTSC station, RXD signal (ch 1) from the Q box is not present.
PM3394, FLUKE & PHILIPS
CH1
T
1
CH2
2
CH1!2.00 V=
CH2!2.00 V=
Waveform 10-1 – Microprocessor Communications* QM – B Board
Signal Name
RXD to Main
IC001 (B Bd)
TXD
MTB2.00ms- 5.82dv ch1-
Location
Micro CN8801/pin B11
CN8801/pin A11
37
10. Communications
Vp-p
3Vp-p
5Vp-p