Specifications

CHAPTER 1
Overview of the AppleVision 1710AV and 1710 Displays
New Display Connections Specifications 17
The displays return the RGB 13” Type 6 (“straight 6”) sense code. (Refer to Macintosh
New Technical Notes HW30 Sense Lines for more information.) This sense code specifies
that sense line 0 is connected to ground, and that sense lines 1 and 2 are unconnected.
These sense lines, therefore, may be conveniently used by DDC, subject to the following
restrictions:
■ When they are powered up, the displays start in DDC1 mode. The 24LC21 serial
EEPROM is ready to clock out one bit of data on sense line 1 (SDA), whenever an
edge transition occurs on VSYNC. However, no data is being clocked at this stage,
since VSYNC starts after sense determination. This is an important sequence, because
if data were being clocked out during sense determination, the Macintosh computer
would probably get an incorrect sense reading.
■ The computer reads the Type 6 (straight 6) sense of the display. It then goes through a
process to determine the level of the Extended Type 6 sense line. As part of this
process, the Macintosh pulls sense line 2 low to check if sense lines 1 or 0 are wired to
sense line 2. It pulls sense line 1 low to check if sense lines 2 or 0 are wired to sense
line 1. At this moment, the 24LC21 EEPROM, detecting that sense line 1 (SDA) is
being pulled low externally, automatically switches to DDC2B mode. In this mode, the
24LC21 waits for sense line 2 (SCL) to go low to clock out the first data bit. However,
on a graphics device that does not support DDC2B, nothing happens, since sense line
2 has already been pulled low to check for the extended sense code. A graphics device
that does support DDC2B is now free to clock out the DDC data.
IMPORTANT
This scheme does not allow “hot-plugging” of video cables. That is, it
does not allow you to plug in the video cable after the Macintosh has
booted. Be sure to shut down the display before plugging in the video
cable or unplugging it. ▲
The video cable pinouts are listed in Table 2-1 on page 21.
Tips for Developers 1
This section contains miscellaneous information to assist software developers who are
supporting smart displays.
IMPORTANT
You do not need to know that a smart display, such as the AppleVision
1710 is attached to your computer. The AppleVision 1710 looks like a 13”
RGB display to the video card, and the card does not need to know that
it is anything different. If you support invalid timing modes for any
sense code, you should add them. The display will adjust the timings to
match the timings it supports. ▲
IMPORTANT
You do not need to add new functional sResources. ▲
You should note the following items:
■ Support wiggling (tagging). Wiggling is part of the cscGetConnection call. It is
documented in Chapter 11 of Designing PCI Cards and Drivers.