HP Palmtop Hardware set

The HP palmtop is a Personal Computer with built-in features that provide industry standard spread-sheet processing, and several Personal Information Management (PIM) applications including a full featured financial calculator. It features an 80186 processor and a hardware set that is moderately compatible with an IBM XT. The HP palmtop has 2 MB of ROM and 1 or 2 MB of RAM built-in, and 1 card port to support PCMCIA plug-in cards.

The LCD display has a resolution of 640x200 dots and supports both MDA and CGA compatible display operation except that "shades of grey" emulate "color." Several different-sized fonts are used to optimize the use of the display, yet retain CGA compatibility.

Several types of graphics modes, including 640x200 Black & White, 320x200 with 4-shade grey scale, and an HP 95LX-compatible 240x128 Black & White (centered in a 320x200 display), are supported. In addition, some non-standard hardware support is provided for rapid display of textual information in Graphics mode. Several different-sized fonts are used by the built-in applications for display of text in Graphics mode.

HP palmtops have improved hardware support (over the HP 95LX) for serial I/O with a 9-pin connection and 16450 compatible UART.

Some differences between HP palmtop and XT hardware are listed below:

• The HP palmtop CGA compatible video mode does not have color.
• The HP palmtop MDA compatible video mode is a 40x16 zoom mode into an 80x25 page.
• The HP palmtop supports "soft fonts" and has BitBlt hardware.
• The HP palmtop has no mechanical disk. Instead, there is a built-in RAM disk and a built-in ROM disk.
• The HP palmtop has a different keyboard layout from the IBM-XT.
• The HP palmtop keyboard management is different from the IBM-XT. Keyboard scans are implemented by an 8048 microcontroller in an XT, while the HP palmtop emulates this action in software.
• The HP palmtop supports plug-in ROMs.
• The HP palmtop supports plug-in RAMs. All memory in plug-in RAM and part of the built-in memory is used as RAM disk.
• The HP palmtop is switched on or off under software control. This is compared to an XT which is switched on or off by a hardware switch that controls power to the entire machine.
• The HP palmtop implements LCD contrast adjustment under software control. This is fundamentally different from XT brightness control, which is done with a potentiometer adjustment.
• The HP palmtop does not support a parallel printer. However, it does support a serial printer which uses XON/XOFF flow control.
• The HP palmtop supports only one serial port UART. However the serial channel can be directed either to the IR or wired serial port.
• There is no parity bit in HP palmtop RAM. The NMI parity error detection in the IBM XT is not present in the HP palmtop.
• The HP palmtop hardware interrupt set is not identical in function to an XT.
• Some XT compatibles have Real Time Clock services. The HP palmtop provides a set of Real Time Clock Time/Date/Alarm services supported in hardware by a 26-bit, 1 Hz timer.