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HP Dc7700 HP Compaq dx7300 and dc7700 Business PC Technical Reference Guide, 1 - Page 71

Real-Time Clock and Configuration Memory, 4.4.1 Clearing CMOS

UPC - 882780715318

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System Support 4.4 Real-Time Clock and Configuration Memory The Real-time clock (RTC) and configuration memory (also referred to as "CMOS") functions are provided by the 82801 component and is MC146818-compatible. As shown in the following figure, the 82801 ICH8 component provides 256 bytes of battery-backed RAM divided into two 128-byte configuration memory areas. The RTC uses the first 14 bytes (00-0Dh) of the standard memory area. All locations of the standard memory area (00-7Fh) can be directly accessed using conventional OUT and IN assembly language instructions through I/O ports 70h/71h, although the suggested method is to use the INT15 AX=E823h BIOS call. 0Dh Register D 0Ch Register C 0Bh Register B 0Ah Register A 09h Year 08h Month 07h Date of Month 06h Day of Week 05h Hours (Alarm) 04h Hours (Timer) 03h Minutes (Alarm) 02h Minutes (Timer) 01h Seconds (Alarm) 00h Seconds (Timer) 82801 FFh Extended Config. Memory Area (128 bytes) 80h 7Fh Standard Config. Memory Area (114 bytes) 0Eh RTC Area 0Dh (14 bytes) 00h CMOS Figure 4 11. Configuration Memory Map A lithium 3-VDC battery is used for maintaining the RTC and configuration memory while the system is powered down. During system operation a wire-Ored circuit allows the RTC and configuration memory to draw power from the power supply. The battery is located in a battery holder on the system board and has a life expectancy of three or more years. When the battery has expired it is replaced with a Renata CR2032 or equivalent 3-VDC lithium battery. 4.4.1 Clearing CMOS The contents of configuration memory (including the Power-On Password) can be cleared by the following procedure: 1. Turn off the unit. 2. Disconnect the AC power cord from the outlet and/or system unit. 3. Remove the chassis hood (cover) and insure that no LEDs on the system board are illuminated. 4. On the system board, press and hold the CMOS clear button (colored yellow) for at least 5 seconds. 5. Replace the chassis hood (cover). 6. Reconnect the AC power cord to the outlet and/or system unit. 7. Turn the unit on. To clear only the Power-On Password refer to section 4.5.1. Technical Reference Guide www.hp.com 4-19

Section	Page
Title	1
Contents	3
Chap_1_Introduction_final_review.pdf	7
Introduction	7
1.1 About this Guide	7
1.1.1 Online Viewing	7
1.1.2 Hardcopy	7
1.2 Additional Information Sources	7
1.3 Model Numbering Convention	7
1.4 Serial Number	9
1.5 Notational Conventions	9
1.5.1 Values	9
1.5.2 Ranges	9
1.5.3 Register Notation and Usage	9
1.5.4 Bit Notation and Byte Values	9
1.6 Common Acronyms and Abbreviations	10
Chap_2_System_Overview_final.pdf	17
System Overview	17
2.1 Introduction	17
2.2 Features	18
2.3 Mechanical Design	20
2.3.1 Cabinet Layouts	21
2.3.2 Chassis Layouts	26
2.3.3 Board Layouts	30
2.4 System Architecture	33
2.4.1 Intel Processor Support	35
2.4.2 Chipset	36
2.4.3 Support Components	37
2.4.4 System Memory	37
2.4.5 Mass Storage	38
2.4.6 Serial and Parallel Interfaces	38
2.4.7 Universal Serial Bus Interface	38
2.4.8 Network Interface Controller	38
2.4.9 Graphics Subsystem	39
2.4.10 Audio Subsystem	39
2.5 Specifications	40
Chap_3_Processor_final_review.pdf	45
Processor/Memory Subsystem	45
3.1 Introduction	45
3.2 Intel Pentium Processors	46
3.2.1 Intel Processor Overview	46
3.2.2 Processor Upgrading	48
3.3 Memory Subsystem	48
Chap_4_System_Support_final_review.pdf	53
System Support	53
4.1 Introduction	53
4.2 PCI Bus Overview	53
4.2.1 PCI 2.3 Bus Operation	54
4.2.2 PCI Express Bus Operation	58
4.2.3 Option ROM Mapping	60
4.2.4 PCI Interrupts	60
4.2.5 PCI Power Management Support	60
4.2.6 PCI Connectors	61
4.3 System Resources	63
4.3.1 Interrupts	63
4.3.2 Direct Memory Access	68
4.4 Real-Time Clock and Configuration Memory	71
4.4.1 Clearing CMOS	71
4.4.2 Standard CMOS Locations	72
4.5 System Management	72
4.5.1 Security Functions	72
4.5.2 Power Management	74
4.5.3 System Status	75
4.5.4 Thermal Sensing and Cooling	75
4.6 Register Map and Miscellaneous Functions	76
4.6.1 System I/O Map	76
4.6.2 SCH5317 I/O Controller Functions	77
Chap_5_Input-Output_Interfaces_final_review.pdf	79
Input/Output Interfaces	79
5.1 Introduction	79
5.2 SATA Interfaces	79
5.2.1 SATA Programming	79
5.2.2 SATA Connector	81
5.2.3 RAID Functionality	81
5.3 Diskette Drive Interface	82
5.3.1 Diskette Drive Programming	82
5.3.2 Diskette Drive Connector	86
5.4 Serial Interface	87
5.4.1 Serial Connector	87
5.4.2 Serial Interface Programming	87
5.5 Parallel Interface	89
5.5.1 Standard Parallel Port Mode	89
5.5.2 Enhanced Parallel Port Mode	89
5.5.3 Extended Capabilities Port Mode	90
5.5.4 Parallel Interface Programming	90
5.5.5 Parallel Interface Connector	92
5.6 Keyboard/Pointing Device Interface	93
5.6.1 Keyboard Interface Operation	93
5.6.2 Pointing Device Interface Operation	95
5.6.3 Keyboard/Pointing Device Interface Programming	95
5.6.4 Keyboard/Pointing Device Interface Connector	99
5.7 Universal Serial Bus Interface	100
5.7.1 USB Data Formats	101
5.7.2 USB Programming	102
5.7.3 USB Connector	103
5.7.4 USB Cable Data	104
5.8 Audio Subsystem	105
5.8.1 HD Audio Controller	106
5.8.2 HD Audio Interface	106
5.8.3 HD Audio Codec	107
5.8.4 Audio Programming	108
5.8.5 Audio Specifications	110
5.9 Network Interface Controller	111
5.9.1 Wake-On-LAN Support	112
5.9.2 Alert Standard Format Support	112
5.9.3 Power Management Support	112
5.9.4 NIC Programming	113
5.9.5 NIC Connector	113
5.9.6 NIC Specifications	114
Chap_6_Integrated_Graphics_final_review.pdf	115
Integrated Graphics Subsystem	115
6.1 Introduction	115
6.2 Functional Description	116
6.3 Display Modes	118
6.4 Upgrading Graphics	119
6.5 VGA Monitor Connector	120
Chap_7_Power_and_Signal_final_review.pdf	121
Power and Signal Distribution	121
7.1 Introduction	121
7.2 Power Supply Assembly/Control	121
7.2.1 Power Supply Assembly	122
7.2.2 Power Control	124
7.2.3 Power Management	127
7.3 Power Distribution	128
7.4 Signal Distribution	131
Chap_8_BIOS_ROM_final_review.pdf	135
BIOS ROM	135
8.1 Introduction	135
8.2 ROM Flashing	136
8.2.1 Upgrading	136
8.2.2 Changeable Splash Screen	137
8.3 Boot Functions	137
8.3.1 Boot Device Order	137
8.3.2 Network Boot (F12) Support	138
8.3.3 Memory Detection and Configuration	138
8.3.4 Boot Error Codes	139
8.4 Setup Utility	140
8.5 Client Management Functions	149
8.5.1 System ID and ROM Type	150
8.5.2 Temperature Status	150
8.5.3 Drive Fault Prediction	150
8.6 SMBIOS	151
8.7 USB Legacy Support	151
App_A_Error_Messages__amp__Codes_final_review.pdf	153
A.1 Introduction	153
A.2 Beep/Power LED Codes	153
A.3 Power-On Self Test (POST) Messages	154
A.4 System Error Messages (1xx-xx)	157
A.5 Memory Error Messages (2xx-xx)	158
A.6 Keyboard Error Messages (30x-xx)	159
A.7 Printer Error Messages (4xx-xx)	160
A.8 Video (Graphics) Error Messages (5xx-xx)	160
A.9 Diskette Drive Error Messages (6xx-xx)	161
A.10 Serial Interface Error Messages (11xx-xx)	162
A.11 Modem Communications Error Messages (12xx-xx)	163
A.12 System Status Error Messages (16xx-xx)	164
A.13 Hard Drive Error Messages (17xx-xx)	165
A.14 Hard Drive Error Messages (19xx-xx)	167
A.15 Video (Graphics) Error Messages (24xx-xx)	168
A.16 Audio Error Messages (3206-xx)	168
A.17 DVD/CD-ROM Error Messages (33xx-xx)	169
A.18 Network Interface Error Messages (60xx-xx)	169
A.19 SCSI Interface Error Messages (65xx-xx, 66xx-xx, 67xx-xx)	170
A.20 Pointing Device Interface Error Messages (8601-xx)	171
App_B_ASCII_Character_Set_final_review.pdf	173
B.1 Introduction	173
App_C_Keyboard_final_review.pdf	177
C.1 Introduction	177
C.2 Keystroke Processing	177
C.2.1 PS/2-Type Keyboard Transmissions	179
C.2.2 USB-Type Keyboard Transmissions	180
C.2.3 Keyboard Layouts	180
C.2.4 Keys	183
C.2.5 Keyboard Commands	186
C.2.6 Scan Codes	187
C.3 Connectors	193

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Technical Reference Guide

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4-19

System Support

4.4 Real-Time Clock and Configuration Memory

The Real-time clock (RTC) and configuration memory (also referred to as “CMOS”) functions

are provided by the 82801 component and is MC146818-compatible. As shown in the following

figure, the 82801 ICH8 component provides 256 bytes of battery-backed RAM divided into two

128-byte configuration memory areas.

The RTC uses the first 14 bytes (00-0Dh) of the standard

memory area. All locations of the standard memory area (00-7Fh) can be directly accessed using

conventional OUT and IN assembly language instructions through I/O ports 70h/71h, although

the suggested method is to use the INT15 AX=E823h BIOS call.

Figure 4 11.

Configuration Memory Map

A lithium 3-VDC battery is used for maintaining the RTC and configuration memory while the

system is powered down. During system operation a wire-Ored circuit allows the RTC and

configuration memory to draw power from the power supply. The battery is located in a battery

holder on the system board and has a life expectancy of three or more years. When the battery

has expired it is replaced with a Renata CR2032 or equivalent 3-VDC lithium battery.

4.4.1 Clearing CMOS

The contents of configuration memory (including the Power-On Password) can be cleared by the

following procedure:

1. Turn off the unit.

2. Disconnect the AC power cord from the outlet and/or system unit.

3. Remove the chassis hood (cover) and insure that no LEDs on the system board are

illuminated.

4. On the system board, press and hold the CMOS clear button (colored yellow) for at least 5

seconds.

5. Replace the chassis hood (cover).

6. Reconnect the AC power cord to the outlet and/or system unit.

7. Turn the unit on.

To clear only the Power-On Password refer to section 4.5.1.

RTC Area

(14 bytes)

Standard Config.

Memory Area

(114 bytes)

Extended Config.

Memory Area

(128 bytes)

00h

0Dh

0Eh

80h

FFh

7Fh

Seconds (Timer)

Minutes (Timer)

Seconds (Alarm)

Hours (Alarm)

Hours (Timer)

Minutes (Alarm)

Day of Week

Date of Month

Month

Year

00h

0Bh

01h

02h

03h

04h

05h

06h

07h

08h

09h

0Ah

0Dh

0Ch

82801

CMOS