Input/Output Interfaces

5.5Parallel Interface Support

These systems include a system board header (P125) that supports an optional parallel bracket/cable assembly that provides a parallel interface for a peripheral device such as a printer. The parallel interface supports bi-directional 8-bit parallel data transfers with a peripheral device. The parallel interface supports three main modes of operation:

Standard Parallel Port (SPP) mode

Enhanced Parallel Port (EPP) mode

Extended Capabilities Port (ECP) mode

These three modes (and their submodes) provide complete support as specified for an IEEE 1284 parallel port.

5.5.1 Standard Parallel Port Mode

The Standard Parallel Port (SPP) mode uses software-based protocol and includes two sub-modes of operation, compatible and extended, both of which can provide data transfers up to 150 KB/s. In the compatible mode, CPU write data is simply presented on the eight data lines. A CPU read of the parallel port yields the last data byte that was written.

5.5.2 Enhanced Parallel Port Mode

In Enhanced Parallel Port (EPP) mode, increased data transfers are possible (up to 2 MB/s) due to a hardware protocol that provides automatic address and strobe generation. EPP revisions 1.7 and 1.9 are both supported. For the parallel interface to be initialized for EPP mode, a negotiation phase is entered to detect whether or not the connected peripheral is compatible with EPP mode. If compatible, then EPP mode can be used. In EPP mode, system timing is closely coupled to EPP timing. A watchdog timer is used to prevent system lockup.

5.5.3 Extended Capabilities Port Mode

The Extended Capabilities Port (ECP) mode, like EPP, also uses a hardware protocol-based design that supports transfers up to 2 MB/s. Automatic generation of addresses and strobes as well as Run Length Encoding (RLE) decompression is supported by ECP mode. The ECP mode includes a bi-directional FIFO buffer that can be accessed by the CPU using DMA or programmed I/O. For the parallel interface to be initialized for ECP mode, a negotiation phase is entered to detect whether or not the connected peripheral is compatible with ECP mode. If compatible, then ECP mode can be used.

The ECP mode includes several sub-modes as determined by the Extended Control register. Two submodes of ECP allow the parallel port to be controlled by software. In these modes, the FIFO is cleared and not used, and DMA and RLE are inhibited.

 

Technical Reference Guide

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HP dc5850 manual Parallel Interface Support, Standard Parallel Port Mode, Enhanced Parallel Port Mode

dc5850 specifications

The HP dc5850 is a desktop computer that was designed for business environments, offering a blend of performance, reliability, and efficiency. Released during the height of the mid-2000s, this system is powered by AMD processors, particularly the Athlon or Phenom series, which ensures that it can handle various computational tasks with ease.

The dc5850 features a compact chassis that adheres to the Microtower form factor. This design not only saves space but also allows for easier upgrades and maintenance. The unit typically supports a range of RAM configurations, with options for up to 8GB of DDR2 memory. This flexibility enables the user to tailor the system's performance according to their needs, whether for basic office tasks or more demanding applications.

Storage options on the HP dc5850 include a 3.5-inch HDD that can accommodate substantial data, with capacities typically ranging from 160GB to 1TB. The inclusion of a SATA interface ensures fast data transfer rates, which is essential for improving overall system performance. Moreover, the dc5850 boasts multiple USB ports, including USB 2.0 and sometimes even USB 3.0, facilitating easy connectivity with peripherals such as printers, scanners, and external drives.

Graphics capabilities on the dc5850 are generally provided by integrated solutions, although users have the option to add discrete graphics cards for enhanced performance in visual tasks. The system often comes with integrated audio, which supports basic multimedia needs without requiring additional sound cards.

In terms of connectivity, the HP dc5850 features built-in Ethernet for wired networking and may also offer options for Wi-Fi capabilities via PCI expansion slots. This makes it suitable for networked business environments, enabling seamless integration into office infrastructures.

The system is designed with energy efficiency in mind, complying with various environmental standards, thereby reducing its carbon footprint. This aspect may also lead to lower operational costs for businesses focused on sustainability.

Overall, the HP dc5850 stands out as a versatile desktop solution, catering to the essential needs of small to medium-sized businesses. With its combination of performance, expandability, and energy efficiency, it remains a noteworthy choice for users seeking reliable computing power in a compact and manageable form.