Дополнительное Руководство для IBM 560z
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)
(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.
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.
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
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.
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
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