January 21, 2005 ELANSC 4 i386

### NAME

elansc - AMD Elan SC520 System Controller driver

### SYNOPSIS

elansc* at mainbus? bus ? gpio* at elansc? pci* at elansc? elanpar* at elansc? elanpex* at elansc?

### DESCRIPTION

The elansc driver supports the system controller of the AMD Elan SC520 microcontroller. The SC520 consists of an AMD Am5x86 processor core, integrated PCI host controller, and several standard on-chip devices, such as NS16550-compatible UARTs, real-time clock, and timers.

The Elan SC520 also provides several special on-chip devices. The following are supported by the elansc driver:

- Watchdog timer. The watchdog timer may be configured for a 1 second, 2 second, 4 second, 8 second, 16 second, or 32 second expiration period.

- PCI exceptions reporting. The SC520 microcontroller can report exceptions that occur as it acts as both a PCI bus master and a bus target. See elanpex(4).

- RAM write-protection. The SC520 microcontroller can designate write-protected regions of RAM using the Programmable Address Regions registers. See elanpar(4).

- Programmable Input/Output. The SC520 microcontroller supports 32 programmable I/O signals (PIOs) that can be used on the system board to monitor signals or control devices that are not handled by the other functions in the SC520 microcontroller. These signals can be programmed to be inputs or to be driven ``high'' or ``low'' as outputs. Pins can be accessed through the gpio(4) framework. The gpioctl(8) program allows easy manipulation of pins from userland.

- PCI host-bridge optimization. elansc takes advantage of a suspend/resume cycle to tune the PCI host-bridge for higher performance.

### SEE ALSO

elanpar(4), elanpex(4), gpio(4), gpioctl(8), wdogctl(8)

### HISTORY

The elansc device first appeared in NetBSD2.0. PIO function support was added in OpenBSD3.6, and subsequently ported to NetBSD4.0. Support for PCI exceptions reporting and for RAM write-protection first appeared in NetBSD5.0.

### AUTHORS

The elansc driver was written by Jason R. Thorpe <thorpej@NetBSD.org>
. Jasper Wallace
provided the work-around for a hardware bug related to the watchdog timer in some steppings of the SC520 CPU. Support for the PIO function was added to OpenBSD3.6 by Alexander Yurchenko <grange@openbsd.org>
and was ported to NetBSD by Jeff Rizzo <riz@NetBSD.org>
. David Young <dyoung@NetBSD.org>
added support for PCI exceptions reporting and for RAM write-protection using the Programmable Address Regions.