, , , . I²C DIMM, . SMBus, I²C. , Xeon. CNR ( ) - . I²C, VESA DDC1/2B, ( ). DDC 15- VGA, EVC P&D, DVI DFP. DDC1/2AB ACCESS.Bus , ( ). (, ), , - . . ACCESS.Bus, I²C, DEC , ( VESA DDC), (Smart Battery) . . I²C (firmware) () . I²C 100 400 /, RS-232C 115 / , / PnP. PC , 3,4 /, .
SMI , Fast Ethernet, ( ).
SPI JTAG , , ( ). , .
I²C
I²C, Philips , . , , . I²C . , . I²C ACCESS.bus SMBus, ( I²C . . 7.3.3).
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I²C
Inter IC Bus ( ), , , I²C, , . 8- . , , . , , , N-, +5 , (3,3 ). I²C, , . . , , I²C, .
I²C , 1.0 1992 . () , ( ) . (Low speed), Standard Mode (S) 0-100 /. 1.0 Fast Mode (F) 0-400 / . 10- . 2.0 1998 ., I²C , . High speed (Hs), 3,4 /. F S , F/S. 2 . 2.1 (2000 .) , Hs. I²C 2.1, www.philips.com. . 11.1.4, SMBus ACCESS.Bus.
I²C : SDA (Serial Data) SCL (Serial Clock). (master) (slave). , . ( ).
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F/S . 11.1. , . ( ), SCL . Ȼ: , , , . (Idle, ) . , , , .
. 11.1. I²C
Start , , ( SCL SDA). Start ( S) SDA SCL. SDA SCL Stop ( P), . SDA SCL, SCL , Stop, repeated Start ( , Sr). S Sr . 8 , ( MSB ), . Ack, , . , SCL . F/S , SCL , . SCL , SCL: , ( ) , , SCL ( ). . SCL , . SCL : , , ( ); .
() , ( ) , , ( ) . SCL SDA . , ( ), SDA ( ), SCL SDA ( SCL ). . , . , , ( Ethernet). , , , , .
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ACK, - , . , () ACK, . ACK ( ) . . , Stop, . , ACK , . ACK SDA SCL, P Sr.
I²C. , . S Sr (. 11.1). , Start, ; , P Sr. 7 , 10- , 7-. 7-, 10- .
11.1. I²C
[7:1] | 0 (RW) | |
0000000 | 0 | General call address |
0000 000 | 1 | Start |
0000 001 | X | CBUS ( ) |
0000 010 | X | |
0000 011 | X | |
0000 1XX | X | Hs |
1111 1XX | X | |
1111 0XX | X | 10- |
7- S (Sr) 7 ([6:0] [7:1]) RW ( 0 RW=1 , RW=0 ). , . Philips. , , 7- : 4 [6:3] (EEPROM 1010), 3 [0:2] . I²C , 1 0 , , .
, , RW=0. (ACK=0), , .
, RW=1. (ACK=0), . , .
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P, , . , , (Sr), .
, I²C ( ) . , . .
, . 11.1, .
♦ , , (. ).
♦ Start I²C ( , ). Start . SDA (. 11.2) , I²C. () .
♦ CBUS ( I²C) I²C .
♦ 10- [2:1] , 10- .
. 11.2. ́ Start
, , . =0 , , , ( 00000110b) (000000100b) . . , ( ). =1 . 7 ( , ), , . ( , ) ( ), .
, , , , . : ( ) , ( ) , .
10- : 7- 112 , 10- 1024 . 10- : S (Sr) 2:1 , 0 RW=0; 8 , . . , RW . 10- : 10- 2 , . Sr 10- (RW=1) . , 2 , Sr, . , 7- . : 10- , Sr . ( Sr) 7- 10- . 10- , 7-, ( 8 ).
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(Hs) 3,4 /, Hs (F/S). , . SDAH SCLH; Hs SDA SCL ( F/S ). Hs F/S; ( ), SCLH (2:1). . Hs ( S) 00001, xxx . ( F/S) , . Hs , Hs ( 000 ), . Hs, . Hs (Sr). , F/S, . Hs , Sr, Hs P, F/S.
ACCESS.Bus
ACCESS.Bus (Accessory Bus) DEC , , (, -), ( VESA DDC). ACCESS.Bus 1991 .; , , (Smart Battery) . . SM (System Management), SMBus, I²C. 125 ( ). I²C ACCESS.Bus , . / . ACCESS.bus Specifications Version 3.0 ACCESS.bus Industry Group 1995 ., .
I²C ( 100 /) 7- . . ACCESS.bus , . , () (). SMBus Sr.
, .
(Off-board ACCESS.bus), , 4- (MOLEX SEMCONN AMP SDL), . 11.2. - 5 50-1000 . ( ), I () (). ( 1000 ) . (125 ) . ( ) 10 . I²C SDA SCL 6 ( ). SDA SCL 51 . , GND +5 .
11.2. ACCESS.bus
1 | GND | |
2 | SDA | |
3 | +5 ( ) | |
4 | SCL |
VESA ACCESS.Bus , 5- ACCESS.Bus; . 11.3.
11.3. ACCESS.Bus (VESA)
1 | GND |
2 | |
3 | SDA |
4 | +5 ( ) |
5 | SCL |
(On-board ACCESS.bus) (350 ); . . 1995 ., SMBus, , SMBus.
ACCESS.bus 3.0 : PA (Programmable Address) FA . ( , ) . PA; FA SM- (System Management). FA SMBus, , PEC . SM Write Word (. ). PA (. ). ACCESS.bus -: ; - (. ). 0110 111; . ( ).
, . 11.3. DestAddr ( I²C). SrcAddr ( , ). P : P=0 (Device Data Stream); P=1 / (control/status). Length ( ); (Body) . Checksum XOR ( ) . XOR . . 4, 131 (127 4 ). , .
. 11.3. ACCESS.Bus
, . , , I²C 7- RW, ACCESS.bus. 50h -, 10h SM-. 6Eh , . 02-4; 52-GCh; 70-FEh 125 , SM- .
ACCESS.bus 9 ( P=1), (). .
.
♦ Reset . F0h. , - . , .
♦ Identification Request . F1h.
♦ Assign Address , , . ( 30) F2h, 28- , .
♦ Capabilities Request . F3h 16- . , ( ), .
♦ Enable Application Report . F5h : 00h , 01 .
♦ Presence Check . F7h ( ).
.
♦ Attention ( ). E0h.
♦ Identification Reply . ( 29) E1h, 28- .
♦ Capabilities Reply . ( 3-35) E3h, 16- (. ) (0-32 ). , .
, , ( P=1).
♦ Resource Request ( ). E5h - . ; ; , ; ( ); .
♦ Resource Grant , . F4h .
♦ Application Hardware Signal -. A0h :
1 Reset ;
2 Halt ;
3 Attention ( ).
♦ Application Test ( B1h).
♦ Application Test Reply . A1h (0 , ) 0-30 .
♦ Application Status Message ( ). A2h , 2 . :
00 ;
01 ;
02 ;
03 ;
04 (, ).
♦ Device Power Management Command . F6 :
00 Run;
01 Standby;
02 Suspend;
03 Shutdown;
04 ;
05 ;
06 .
. , P=0.
ACCESS.bus 28 (protocol revision), 7- (module revision), 8- (vendor name) (module name), 32- (device number). ( , ), , ( ). , , (Capabilities) ( ) . .
: , . , . , ( ). - Attention, .
ACCESS.bus -. ACCESS.bus Manager , , . , , - MPD; , . , ( -). , . ( ) , , . - MPD (Mini Port Driver) -. . ACCESS.bus (Device Driver, Mini Port Driver), , (Locator), , .
SMBus
SMBus (System Management Bus ) , . . , SMBus Smart Battery System Specifications ( ). , , (Smart Battery System) () , -, . ( , ), ( -) . , . SMBus 1995 ., 1.1 1998 . 2.0 2000 ., . System Management Bus (SMBus) Specification Version 2.0, (SBS, www.sbs-forum.org), , Intel. (OSI), .
SMBus I²C, . 11.1.1. ( ) . I²C (. . 11.1.4), . , I²C, . SMBus BIOS . SMBus, , , ( ) . , BIOS , BIOS .
(1- OSI) . ( ) . (low power) SMBus ; . (high power) SMBus (, PCI). , . , .
. (10 ), (100 ); . -, , , . I²C .
SMBus .
♦ SMBSUS# . ; ( ) SDA SCL ( I²C) ( ).
♦ SMBALERT# , . Ȼ . , 0001 100, ( PEC).
(2- OSI) , I²C: S, P, Sr; ; 7- RW , S (Sr). I²C, , ; ( Sr). SMBus . ACK, . . NACK , . ( ). NACK . NACK ( P). , , NACK .
(3- OSI) SMBus .
SMBus
SMBus (host) , . , .
; 7- (. 11.4), , I²C. 10- . . SMBus WG (Purpose-assigned addresses). , Smart Battery 0001 011, 0001 001. SMBus, . SMBus , . , . , , SMBus , , www.smbus.org. - - . SMBus 2.0 , .
11.4. SMBus
[7:1] | 0 (RW) | |
0000 000 | 0 | General call address |
0000 000 | 1 | Start |
0000 001 | X | CBUS ( ) |
0000 010 | X | |
0000 011 | X | , |
0000 1XX | X | |
0101 000 | X | ACCESS.bus |
0110 111 | X | ACCESS.bus |
1111 0XX | 10- | |
1111 1XX | X | |
0001 000 | X | SMBus |
0001 100 | X | SMBus |
1100 001 | X | SMBus |
1001 0XX | - |
SMBus , . , . 11 , SMBus.
1.1 SMBus PEC (Packet error checking). PEC CRC-, , . PEC PEC; PEC, . PEC , . PEC NACK, , . ACK : PEC ; . . , , PEC, .
SMBus I²C 7- .
♦ Quick Command, , ; RW .
♦ Send Byte, , (RW=0) . PEC , PEC.
♦ Receive Byte, , (RW=1) . PEC , PEC.
♦ Write Byte, Write Word, /, (RW=0) , 1 2 (, ) . PEC .
♦ Read Byte, Read Word, /, : (RW=0), . , 5 , RW=1, 1 2 . PEC () .
♦ Block Write, , (RW=0) , - ( ) . PEC . PEC; ; 32 .
♦ Block Read, , : (RW=0), . , S , RW=1, - , . PEC () . .
♦ Process Call, , Write Word ( ) . , , . PEC , .
♦ Block Write-Block Read Process Call . PEC , .
, ( ), (SMBus host notify protocol): RW=0 ( ) , ( ) . ; SMBALERT# (. ).