IBM 560 - Manual (Page 43)

Bit 0 When set to 1, this bit enables the daylight-saving-time
mode. When set to 0, this bit disables the
daylight-saving-time mode, and the clock reverts to
standard time. The system initializes this bit to 0.
Status Register C (Hex 00C)
Figure 2-18. Status Register C (Hex 00C)
Bit Function
7 Interrupt request flag
6 Periodic interrupt flag
5 Alarm interrupt flag
4 Update-ended interrupt flag
3–0 Reserved
Note: Interrupts are enabled by bits 6, 5, and 4 in status register B.
Bit 7 When set to 1, this bit indicates that an interrupt has
occurred; bits 6, 5, and 4 indicate the type of interrupt.
Bit 6 When set to 1, this bit indicates that a periodic interrupt
has occurred.
Bit 5 When set to 1, this bit indicates that an alarm interrupt
has occurred.
Bit 4 When set to 1, this bit indicates that an update-ended
interrupt has occurred.
Bits 3–0 These bits are reserved.
Status Register D (Hex 00D)
Figure 2-19. Status Register D (Hex 00D)
Bit Function
7 Valid RAM
6–0 Reserved
Bit 7 This read-only bit monitors the internal battery. When
set to 1, this bit indicates that the real-time clock has
power. When set to 0, it indicates that the real-time
clock has lost power and the data in CMOS is no longer
valid.
Bits 6–0 These bits are reserved.
ThinkPad 560/560E System Board 2-21