IBM ThinkPad 560Z, Дополнительное руководство

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Real-Time Clock Bytes (X
'
000
'
–X
'
00D
'
): Bit definitions and
addresses for the real-time clock bytes are shown in Figure 2-15.
Figure 2-15. Real-Time Clock Bytes (X ' 000 ' –X ' 00D ' )
Address
(Hex)
Function
Byte Number
000 Seconds 0
001 Second alarm 1
002 Minutes 2
003 Minute alarm 3
004 Hours 4
005 Hour alarm 5
006 Day of week 6
007 Date of month 7
008 Month 8
009 Year 9
00A Status register A 10
00B Status register B 11
00C Status register C 12
00D Status register D 13
Note: The setup program initializes status registers A and B when
the time and date are set. Interrupt 1AH is the BIOS
interface to read and set the time and date; it initializes the
registers in the same way that the setup program does.
Status Register A (X
'
00A
'
)
Figure 2-16. Status Register A (X
'
00A
'
)
Bit Function
7 Update in progress
6–4 22-stage divider
3–0 Rate-selection bits
Bit 7 If set to 1, this bit indicates that the time-update cycle is
in progress. If set to 0, it indicates that the current date
and time can be read.
Bits 6–4 These bits identify which time-base frequency is being
used. The system initializes these bits to B
'
010
'
, which
selects a 32.768-kHz time base. This is the only value
supported by the system for proper timekeeping.
Bits 3–0 These bits allow the selection of a divider output
frequency. The system initializes the rate-selection bits
to B
'
0110
'
, which selects a 1.024-kHz square-wave
2-20 ThinkPad 560Z System Board