cmos笔记

Offset 

 Description 

 

0x00 

 Current second (Real Time Clock) 1 

 

0x01 

 Alarm second1 

 

0x02 

 Current minute (Real Time Clock) 1 

 

0x03 

 Alarm minute1 

 

0x04 

 Current hour (Real Time Clock) 1 

 

0x05 

 Alarm hour1 

 

0x06 

 Current day of week (Real Time Clock) 1 

 

0x07 

 Current date of month (Real Time Clock) 1 

 

0x08 

 Current month (Real Time Clock) 1 

 

0x09 

 Current year (Real Time Clock) 1 

 

0x0a 

 RTC Status Register A 

 

0x0b 

 RTC Status Register B 

 

0x0c 

 RTC Status Register C 

 

0x0d 

 RTC Status Register D 

 

0x0e 

 POST diagnostics status byte 

 

0x0f 

 Shutdown status byte 

 

0x10 

 Diskette drive types 

 

0x11 

 Reserved 

 

0x12 

 Hard Disk drive types 

 

0x13 

 Reserved 

 

0x14 

 Equipment byte 

 

0x15 

 Base memory (low byte) 

 

0x16 

 Base memory (high byte) 

 

0x17 

 Extended memory (low byte) 

 

0x18 

 Extended memory (high byte) 

 

0x19-0x2d 

 Reserved 

 

0x2e 

 Check sum (low byte) 

 

0x2f 

 Check sum (high byte) 

 

0x30 

 Extended memory above 1 Mb (low byte) 

 

0x31 

 Extended memory above 1 Mb (high byte) 

 

0x32 

 Current century1 

 

0x33 

 Information Flags 

 

0x34-0x3f 

 Reserved 

 

 

CMOS Registers 

   The CMOS RAM data area consists of two banks of 128 bytes. The first 64 bytes in both bank are the same and contain clock and calendar information. The second 64 bytes in bank 1 control security and system start-up features. 

 

Note: Access to the two banks in CMOS RAM is controlled by the bank-control bit in Status Register A (see Status Register A (Hex 00A)).  

   The following figure shows the addresses and definition for the first 64 bytes of RT/CMOS RAM. 

 

 The CMOS RAM data area consists of two banks of 128 bytes. The first 64 bytes in both bank are the same and contain clock and calendar information. The second 64 bytes in bank 1 control security and system start-up features.

 

RAM Address Map

 RT/CMOS 

 ADDRESS 

  (HEX)        RT/CMOS RAM BYTES 

000-00D       Real-Time Clock bytes

00E           Diagnostic Status byte

00F           Shutdown Status byte

010           Diskette Drive Type byte 

011           First Fixed Disk Drive Type byte 

012, 013      Reserved

014           Equipment byte

015, 016      Low and high Base Memory bytes

017, 018      Low and high Expansion Memory bytes

019-031       Reserved

034           Reserved

035, 036      Low and high usable memory above 1MB

037           Date Century byte

038-07F       Reserved

 

Warning:

The operation that follows a write operation to address hex 0070 must read from address hex 0071; otherwise intermittent malfunctions and unreliable operation of the RT/CMOS RAM can occur.

 

CMOS RAM Bank 0

000-00D Real-Time Clock Bytes 

00A     Status Register A Timer Related

00B     Status Register B Date and Alarm Related

00C     Status Register C Interrupt Related

00D     Status Register D CMOS Valid Byte

 

CMOS RAM Configuration

00E     Diagnostic Status Byte Configuration Related

00F     Shutdown Status Byte Set by power-on diagnostics 

010     FD Type Byte Type of Floppy installed

011     1st Fixed Disk Drive Type Byte Type HD installed

011     2nd Fixed Disk Drive Type Byte Type HD installed

012,013 Reserved Bytes 

014     Equipment Byte #FDs, Display, Co-pro, A: present

015,016 Low and High Base Memory Bytes Memory <640KB

017,018 Low and High Expansion Memory Bytes Memory >1MB

019-031 Reserved Bytes 

032,033 Configuration CRC Bytes CRC data for RTC CMOS

034     Reserved Byte

035,036 Low and High Usable Memory Bytes Memory 1-16MB

037     Date-Century Byte BCD Value for century

038-04F Reserved Bytes

 

CMOS RAM Bank 1

40-47F  System Number System Identifier

48      Century Byte BCD Value for Cenuty

49      Wake-up Alarm Date Date set for Power-On

4A      Extended Control Register A Security and power-on

4B      Extended Control Register B Security and power-on

4C-7F   Reserved