X86 CMOS

1、cmos简介。
cmos是主板上一块可读写的RAM芯片。用途：主要用来保存当前系统的硬件配置和操作人员对某些参数的设定。cmos芯片是由一块纽扣电池供电。因此在关机状态内部信息也不会丢失。

2、cmos所在的端口。
cmos芯片是挂在cpu的io空间上的.(x86体系是独立编址的)。cmos拥有两个端口号分别是70h和71h

端口号权限长度作用
70h 不可读可写 8bit 用它来设置cmos中的数据地址
71h 可读可写 8bit 用它来设置70h端口地址中的值

3、cmos中的数据地址对照表。(供编程时查)
地址数据备注
00H Time - Seconds 硬件时间的秒
01H Alarm - Seconds
02H Time - Minutes 硬件时间的分
03H Alarm - Minutes
04H Time - Hours 硬件时间的时
05H Alarm - Hours
06H Date - Day of the week
07H Date - Day
08H Date - Month
09H Date - Year
0AH Status Register A
0BH Status Register B
0CH Status Register C
0DH Status Register D
0EH Diagnostic Status
0FH Shutdown Status
10H A:
11H Reserved
12H 0
13H Reserved
14H Equipment Installed
15H Base Memory (high byte)
16H Base memory (low byte)
17H Extended Memory (high byte)
18H Extended Memory (low byte)
19H 0 (C:) Hard Disk Type
1AH 1 (D:) Hard Disk Type
1BH Reserved
1CH Supervisor Password
1DH Supervisor Password
1EH ~ 2DH Reserved
2EH CMOS Checksum (high byte)
2FH CMOS Checksum (low byte)
30H Extended Memory (high byte)
31H Extended Memory (low byte)
32H Date - Century
33H Power On Status
34H～3FH Reserved
40H～5FH Extended CMOS
60H User Password
61H User Password
62H～7FH Extended CMOS

4、编程实例

#ifndef _CMOS_H_
#define _CMOS_H_    1#include <io.h>/* CMOS I/O REG */
#define CMOS_ADDR_REG   0x70
#define CMOS_DATA_REG   0x71/* CMOS INDEX */
#define CMOS_INDEX_SECOND       0
#define CMOS_INDEX_SECOND_ALARM 1
#define CMOS_INDEX_MINUTE       2
#define CMOS_INDEX_MINUTE_ALARM 3
#define CMOS_INDEX_HOUR     4
#define CMOS_INDEX_HOUR_ALARM       5
#define CMOS_INDEX_DAY_OF_WEEK      6
#define CMOS_INDEX_DAY_OF_MONTH 7
#define CMOS_INDEX_MONTH        8
#define CMOS_INDEX_YEAR     9#define CMOS_INDEX_STATUS_A 0xA
#define CMOS_INDEX_STATUS_B 0xB
#define CMOS_INDEX_STATUS_C 0xC
#define CMOS_INDEX_STATUS_D 0xD#define CMOS_STATUS_B_DAYLIGHT  1
#define CMOS_STATUS_B_24HOUR    2
#define CMOS_STATUS_B_BINARY    4static inline uint8_t bcd_to_num(uint8_t a)
{return ((a >> 4) * 10 + (a & 0xF));
}static inline uint8_t num_to_bcd(uint8_t a)
{return (((a / 10) << 4) + (a % 10));
}static inline uint8_t cmos_read(uint8_t index)
{outb(CMOS_ADDR_REG, index);return inb(CMOS_DATA_REG);
}static inline void cmos_write(uint8_t index, uint8_t value)
{outb(CMOS_ADDR_REG, index);outb(CMOS_DATA_REG, value);
}#endif /* _CMOS_H_ */