BOB-3 Version 3.4 Application Guide ~ Copyright © 2004 by Decade Engineering ~ Page 5
8
TXD; Transmit data output, 5V logic
9
RXD; Receive data input, 5V logic
10
CPU Reset\ input (low true, usually needed only for factory test)
11
ADC7; Reserved input (should be grounded)
12~14
Baud rate select inputs; defaults to 9600bps if not connected. 4.7K pullup resistors (to pin
3) must be connected to these pins if they’re not tied permanently high or low. See baud
rate table below.
15
Video detector output; low if input video is missing, can drive LED with series resistor of
330~680 ohms to +5V (pin 3).
16
P4/RED Output port (use is optional)
17
Factory test (do not connect)
18
Factory test (do not connect)
19
Factory test (do not connect)
20
P5/CSYNC Output port; CSYNC output function is required for crawl feature, if user
intends to implement it. See “Crawl Mode” topic.
21
Character intensity control input (use is optional). Leave open if unused. Not controlled by
software. See notes for control hookup.
22
Background intensity control input (use is optional). Leave open if unused. Not controlled
by software. See notes for control hookup.
23
Clamped video output (for optional external video mixing circuit)
24
P3/GRN Output port (use is optional)
25
P2/BLU Output port (use is optional)
26
P1/BLKG Output port (use is optional)
27
P0/YM Output port (use is optional)
28
Video output; drives 1Vpp into 75 ohms; see notes.
29
Ground (for video signals); also wire to pin 2 or host board ground plane.
30
Video input; requires 1Vpp into 75 ohms (use is optional).
Notes:
o
Only DC power, data input, and video output connections are mandatory. Video input is necessary for
genlock/overlay functionality. Data input is not necessary if a start-up display (boot script) has been stored
and it is the only required display. See basic hookup diagram.
o
Character and background intensity control inputs (pins 21 & 22) are optional, and may be used to trim
foreground and background brightness. Measure video output with an oscilloscope if precise level settings
are required. Use 10K linear pots, and connect as follows:
1. Counterclockwise end: ground (BOB-3 pin 29)
2. Wiper: BOB-3 pin 21 or 22
3. Clockwise end: +5VDC (BOB-3 pin 3)
o
Decade Engineering recommends the addition of 4.7K pullup (to +5V) resistors at pins 12~14 unless they
are tied permanently high or low for baud rate selection. Weak internal pullups are provided, but wrong
baud rate selection is possible under some conditions if pullup current is not augmented. Strap one or more
pins to ground as required to configure the serial communication rates listed below:
Pin 12
Pin 13
Pin 14
Baud Rate (bps)
Lo Lo Lo
1200
Lo Lo Hi
2400
Hi Lo Hi
4800
Hi Hi Hi
9600
Lo Hi Hi
19,200
Hi Hi Lo
38,400
Lo Hi Lo
76,800
Hi Lo Lo
153,600
