The source-terminated reflected wave switching scheme is a familiar one. One just needs to add a source-series terminator, which added together with the driver's output impedance equals the line impedance.
I have, however, recently seen the following passage in Right the First Time Vol.1 [p.156] by Lee Ritchey and John Zasio:
There is no need for a separate series resistor if the driving voltage source impedance can be controlled to be equivalent to the transmission line impedance. The drive transistor size can be adjusted so that it produces a half amplitude transition into the transmission line. The impedance of the ON drive transistor acts as the termination. Figure 36.5 shows a half-series transmission line with a series terminated driver and load.
I'd like to know:
how this adjusting the drive transistor size is accomplished. I'm assuming the author means on-the-fly adjustment, and not manufacturing adjustment.
I've seen ASICS on which you can select a drive strength. I'd presume this is the same thing, or isn't it? Here's an excerpt from the datasheet of such an ASIC: