JVC 340 SC, 330 Overlay Interface, LED Display Buffers and Logic, RS232 Interface, IR Interface

Chapter 2—Functional Description

each line in the raster. The starting address is timed by the /MAPST signal. When that comes along, it indicates the top of the raster is beginning so the address generator should begin counting at the beginning.

Overlay Interface

The Overlay Interface takes the raw data out of the Overlay Memory and sends formatted information to the VPB for generating the desired displays. Some of the data is simply buffered and sent along. That data is the information regarding the full brightness and external video that produces everything but greyscale and dots. The greyscale, dot, and pyramid patterns must first be decoded by a D to A. After conversion to analog and appropriate filtering, the information is sent out to the VPB as the VIDTEST signal.

LED Display Buffers and Logic

The LED dot matrix display is located on the rear of the projector just under the video and sync input connectors. In that location, it is not physically located on the SCB but it is directly controlled by the CPU with connection via the backplane.

The Dot Matrix Display is used for displaying operational and error codes. These codes will assist in troubleshooting and verifying proper operation. The Dot Matrix Display receives its data from the CPU via the display buffer.

RS232 Interface

The RS232 Interface is a bi-directional communications port. The interface protocol is RS232 with two (2) ports; one (1) port being fully functional with the other having more limited use.

The Terminal In port is the fully functional port. It is used for communicating with the projector using a VT100 or similar terminal emulator. The terminal allows accessing all functions available on the projector. In addition, using the terminal provides the user with continuously updated status data. The bi- directional port allows third-party controllers to be used to control the projector using ASCII character control codes.

The Terminal Out port is also RS232 but has limited functionality. It is used primarily for attaching a switcher to the projector to allow for smoother switching of sources.

IR Interface

The IR Interface is a receive-only interface. There is no capability to transmit information out of the projector over the IR interface. The user must depend on the on-screen information and LED Dot Matrix displays to verify operation of the projector.

Model 330, 340SC and 370SC Service Manual 2-65