HP X Class 500/550MHz, Reference Manual

Page: 61 / 149

Chapter 2 61
System Board
Devices on the ISA Bus
Devices on the ISA Bus
The Super I/O Controller (NS 97317)
The Ultra I/O chip (NS 97317) provides the control for two FDD devices, two serial ports
and one bidirectional multi-mode parallel port.
Serial / parallel communications ports
The 9-pin serial ports (whose pin layouts are depicted in the section “Socket Pin Layouts”
in the chapter “Interface Boards and Mass-Storage Drives”) supports RS-232-C and are
buffered by 16550A UARTs, with 16-Byte FIFOs. They can be programmed as COM1,
COM2, COM3, COM4, or disabled.
The 25-pin parallel port (also depicted in the section “Socket Pin Layouts” in the chapter
“Interface Boards and Mass-Storage Drives”) is Centronics compatible, supporting IEEE
1284. It can be programmed as LPT1, LPT2, or disabled. It can operate in the four
following modes:
• Standard mode (PC/XT, PC/AT, and PS/2 compatible).
• Bidirectional mode (PC/XT, PC/AT, and PS/2 compatible).
• Enhanced mode (enhanced parallel port, EPP, compatible).
• High speed mode (MS/HP extended capabilities port, ECP, compatible).
FDC
The integrated flexible disk controller (FDC) supports any combination of two of the
following: tape drives, 3.5-inch flexible disk drives, 5.25-inch flexible disk drives. It is
software and register-compatible with the 82077AA, and 100% IBM-compatible. It has an
A and B drive-swapping capability and a non-burst DMA option.
RTC
The real-time clock (RTC) is 146818A-compatible, with an accuracy of 20ppm (parts per
million). The configuration RAM is implemented as 256 bytes of CMOS. The RTC operates
on a 32.768 kHz crystal and a separate 3V goldcap that provides up to 3 weeks of
protection when the power cord is unplugged.
The century is stored in a register of the RTC and will automatically change from 1999 to
2000 (without BIOS intervention).
Table 2-10. Devices on the ISA Bus
ISA Device Index Data
Ultra I/O 2Eh 2Fh