ISASET(8) System Manager’s Manual ISASET(8)
isaset – set ISA registers
isaset [-y] [-W|-L] addrreg datareg address value [mask] #for I2C-like
isaset -f [-y] [-W|-L] address value [mask] #for flat address space
isaset is a small helper program to set registers visible through the
-f Enable flat address space mode.
-y Disable interactive mode. By default, isaset will wait for a
confirmation from the user before messing with the ISA bus. When
this flag is used, it will perform the operation directly. This
is mainly meant to be used in scripts.
-W Perform a 16-bit write.
-L Perform a 32-bit write.
OPTIONS (I2C-like access mode)
Four options must be provided to isaset. addrreg contains the ISA
address of the address register for the chip to probe; datareg contains
the address of the data register. Both addresses are integers between
0x0000 and 0x3FFF. Usually, if the chip’s base address is 0x0nn0, the
address register is at 0x0nn5 and the data register is at 0x0nn6. The
most common base address for hardware monitoring chips is 0x0290. For
Super-I/O chips, address register is typically at 0x2E with data regis‐
ter at 0x2F. The address and value parameters are two integers between
0x00 and 0xFF. isaset will write value value to address address. An
optional mask can be provided as a fifth parameter, preserving unmasked
bits at the written location.
OPTIONS (flat address space mode)
In flat mode, two parameters must be provided. address contains the ISA
address of the register to write to; it is an integer between 0x0000
and 0xFFFF. Basically, it is the sum of the chip’s base address and the
chip register’s address. isaset will write value value at this address.
An optional mask can be provided as a third parameter, preserving
unmasked bits at the written location.
Poking around in ISA data space is extremely dangerous. Running isaset
with random parameters can cause system crashes, data loss, and worse!
Be extremely careful when using this program.
Mark D. Studebaker, and the lm_sensors group (http://www.lm-sen‐
This manual page was shamelessly ripped from the i2cset and isadump
manual pages by Jean Delvare.
April 2011 ISASET(8)