BegasBattleNotes

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(Signals from bottom PCB that are sent to Chroma board)
(Signals from bottom PCB that are sent to Chroma board)
Line 40: Line 40:
|-
|-
|B3
|B3
-
|2?
+
|2
|12V
|12V
|-
|-
|A5
|A5
-
|3?
+
|3
|5V
|5V
|-
|-
|B5
|B5
-
|3?
+
|3
|5V
|5V
|-
|-
|A7
|A7
-
|9?
+
|9
|Analog red
|Analog red
|-
|-
|B7
|B7
-
|4?
+
|4
|DSP Sel (I assume this means whether to display laserdisc video or computer generated video)
|DSP Sel (I assume this means whether to display laserdisc video or computer generated video)
|-
|-
|A8
|A8
-
|8?
+
|8
|Analog green
|Analog green
|-
|-
|B8
|B8
-
|5?
+
|5
-
|SUB PC BLKING (related to SG BLK)
+
|SUB PC BLKING aka BL (related to SG BLK)
|-
|-
|A9
|A9
-
|7?
+
|7
|Analog blue
|Analog blue
|-
|-
|B9
|B9
-
|6?
+
|6
|csync
|csync
|-
|-
|A10
|A10
-
|1?
+
|1
|Ground
|Ground
|-
|-
|B10
|B10
-
|10?
+
|10
|Ground
|Ground
|}
|}

Revision as of 23:44, 23 October 2021

Contents

Sync signals

Sync Generation

Video sync signals are generated by what appears to be a custom Sony chip called the CX 773A (I couldn't find any info about this by googling for it). You can find it on the Bega's Battle schematic called "DSP Control Decode" and it is at position 16K on the bottom PCB (the one with the two BNC outputs).

This custom IC takes in a 14.3182 MHZ clock and five of its output are used.

Pin Description Notes
4 Composite Sync Active low. Typical NTSC composite sync. Nothing unusual observed.
6 SG BLK Active low. May refer to "signal block" meaning when to prevent computer generated video from going to the monitor. For top field, starts at beginning of line 1 and ends when line 21 begins, and otherwise goes low when HSync goes low (and lasts a little bit longer than HSync pulses).
8 HSYNC 2 Active low. Appears to run at a constant 15.73 kHz frequency with no variation. Each line is 63.56 uS long. Each pulse lasts for 6.72 uS. Usually starts a little before csync and ends a little after. Goes low at the same time as SG BLK.
11 VSYNC 2 Active low. For top field, starts at the beginning of line 1 and ends at the end of line 9. No apparent delay relative to csync. Each pulse lasts for 0.5721 ms and the frequency is a constant 59.93 Hz, with a period of 16.69 ms.
15 SC Appears to match the color burst frequency. Runs at 3.58 MHz.

Signals from bottom PCB that are sent to Chroma board

CN2 Pin from bottom PCB CN1 Pin on Chroma PCB Description
B3 2 12V
A5 3 5V
B5 3 5V
A7 9 Analog red
B7 4 DSP Sel (I assume this means whether to display laserdisc video or computer generated video)
A8 8 Analog green
B8 5 SUB PC BLKING aka BL (related to SG BLK)
A9 7 Analog blue
B9 6 csync
A10 1 Ground
B10 10 Ground

BNC output voltage levels

BegasBattleBNCOutputs 1SC 2CSync-1.png

Yellow is SC (color burst?). Blue is csync. Blue averages about 2.4V high.

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