Specifications

38 158004.B00
3.17 SERIAL EEPROM
The TP400 has a serial EEPROM chip fitted. This is used primarily to store set-up
parameters in systems that lack a battery to retain configuration data in the CMOS
SRAM. There is some space available in the serial EEPROM for users’ data. The
serial EEPROM chip also contains the watchdog timer, which is also accessed
through the EEPROM's serial interface.
See section 6.7 and 6.8 for information on using the serial EEPROM utility programs.
See section 5.2 for details of the watchdog timer.
3.18 UTILITY REGISTER
The TP400 has a Utility Register that controls a number of peripheral functions
including the serial EEPROM, analog to digital converter interface and Flash memory
programming. The Utility Register is formed by a number of the GPIO pins within the
PC97317 Super I/O chip and appears in the I/O address space. The Utility Register
occupies eight 8-bit I/O locations at addresses 0E0h - 0E7h.
The Utility Register is used extensively by the Flash File System driver software and
the serial EEPROM and analog to digital convertor software, and will not normally be
accessed by the user.
Table 7 gives the function of each bit in the Utility Register.
Following reset all bits are set to logic 1. They have internal pull-up resistors fitted.
The BIOS configures the pins as outputs or inputs. When writing to the registers the
user should read the current state, change only the required bits, and write the results
back. Users should not change bits they do not understand, or the TP400 may stop
working.
Note that two bits are present at address E4h, bit 7. The SO bit is normally present in
this location. The Flash File System software may sometimes change the function of
this bit to BA22, but it will restore the function to that of SO when the flash operation
is complete. (Users who want to fully understand this should read the GPIO section of
the PC97317 Super I/O data sheet, and note that the eight bits at address E0h are
GPIO port 1 (in GPIO bank 0), the next eight bits at address E4h are GPIO Port 2 (in
GPIO bank 0) and the BA22 bit is bit 7 of GPIO Port 3 (in GPIO bank 1), which is also
accessed at address E4h).