Technical data

BIOS and System Programming
CP 486 ⋅ 00/14 VIPA GmbH 69
4.3.6 CMOS-RAM Statusbyte (CMOS-RAM Address 4E)
CMOS-RAM used contains additional memory areas from 40 to 4F. These memory areas are used
by VIPA for BIOS-extensions and for the VIPA-SETUP, and are protected by a checksum. The user
is not allowed to make any changes in this RAM area.
Byte 4E - the VIPA-CMOS status byte - is excepted herefrom. It is assigned as follows:
Bit 0 0 system date and system time are ok
1 system date and system time are lost
Bit 1 0 system configuration is ok
1 system configuration lost, default table was loaded
Bit 2-6 vacant
Bit7 0 mustbesetto0
Procedure:
CP486 always boots also in the case of lost system configuration (discharged battery) because of the
extensions in the VIPA-BIOS. The exact system configuration can be reloaded by DOS, excepted
date and time. These two parameters must be input by the operator in any case if the configuration is
lost. For this purpose, bit 0 in the VIPA-CMOS status register is used. This bit can be inquired and
set by the operator also on standard language level.
The operator is allowed to access to bit 0 and to set this bit to 1 if he has corrected date and time.
This byte is not supervised by the checksum control.