1. Introduction
20
The ZT 5504's Counter/Timers reside in the Intel 82371EB (PIIX4E) device. The "
Intel 440GX
AGPset
" topic in Appendix E provides a link to the datasheet for this device.
DMA
Two enhanced, 8237-style DMA controllers are provided on the ZT 5504 for use by the on-
board peripherals.
The ZT 5504's DMA controllers reside in the Intel 82371EB (PIIX4E) device. The "
Intel 440GX
AGPset
" topic in Appendix E provides a link to the datasheet for this device.
Real-Time Clock
The real-time clock performs timekeeping functions and includes 256 bytes of general-purpose,
battery-backed, CMOS RAM. Timekeeping features include an alarm function, a maskable
periodic interrupt, and a 100-year calendar. The system BIOS uses a portion of this RAM for
BIOS setup information.
The ZT 5504's Real-Time Clock resides in the Intel 82371EB (PIIX4E) device. The "
Intel
440GX AGPset
" topic in Appendix E provides a link to the datasheet for this device.
Reset
The push-button reset on the ZT 5504's faceplate functions as a "Hard Reset". See Chapter 4,
"
Reset
," for more information about reset sources for the ZT 5504.
Two-Stage Watchdog Timer
The watchdog timer optionally monitors system operation and is programmable for one of eight
different timeout periods (from 0.25 seconds to 256 seconds). It is a two-stage watchdog,
meaning that it can be enabled to produce a non-maskable interrupt (NMI) or a "CPU init"
before it generates a Reset. Failure to strobe the watchdog timer within the programmed time
period may result in an NMI, a reset request, or both. A register bit can be enabled to indicate if
the watchdog timer caused the reset event. This watchdog timer register is cleared on power-
up, enabling system software to take appropriate action if the watchdog generated the reboot.
See Chapter 7, "
Watchdog Timer
," for more information, including sample code.
Universal Serial Bus (USB)
The Universal Serial Bus (USB) provides a common interface to slower-speed peripherals.
Functions such as keyboard, serial ports, printer port, and mouse ports can be consolidated
into USB, simplifying cabling requirements. The ZT 5504 provides two USB ports at its
faceplate (connector J8 is Port 0, J9 is Port 1). USB Port 0 can be routed to the ZT 5504's
J5 Rear Panel I/O connector
by reconfiguring
CT57 and CT58
. USB Port 1 can be routed to the
ZT 5504's J5 Rear Panel I/O connector by reconfiguring
CT31 and CT32
.
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