Hardware Reference
In-Depth Information
Enhanced Capabilities Port
In 1992, Microsoft and Hewlett-Packard announced another type of high-speed parallel port: the
Enhanced Capabilities Port (ECP). Similar to EPP, ECP offers improved performance for the
parallel port and requires special hardware logic.
Since the original announcement, ECP was included in IEEE 1284—just like EPP. Unlike EPP,
however, ECP is not tailored to support portable PCs' parallel port peripherals; its purpose is to
support an inexpensive attachment to a high-performance printer or scanner. Furthermore, ECP mode
requires the use of a direct memory access (DMA) channel, which EPP did not define and which can
cause troublesome conflicts with other devices that use DMA. Most PCs built since the mid-1990s
support both EPP or ECP modes. If you use parallel devices, it's recommended that the port be
placed in ECP mode (or a combination mode known as EPP/ECP) for the best throughput.
Parallel Port Configuration
The configuration of parallel ports is not as complicated as it is for serial ports. Even the original
IBM PC had BIOS support for three LPT ports. Table 14.18 shows the standard I/O address and
interrupt settings for parallel port use.
Table 14.18. Parallel Interface I/O Port Addresses and Interrupts
Because the BIOS has always provided three definitions for parallel ports, problems with parallel
ports are infrequent.
 
 
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