May 2006
7
MIC280
MIC280
Micrel
Functional Description
Serial Port Operation
The MIC280 uses standard SMBus Write_Byte, Read_Byte,
and Read_Word operations for communication with its host.
The SMBus Write_Byte operation involves sending the
devices slave address (with the R/W bit low to signal a write
operation), followed by a command byte and the data byte.
The SMBus Read_Byte operation is a composite write and
read operation: the host rst sends the devices slave address
followed by the command byte, as in a write operation. A
new start bit must then be sent to the MIC280, followed by a
repeat of the slave address with the R/W bit (LSB) set to the
high (read) state. The data to be read from the part may then
be clocked out. A Read_Word is similar, but two successive
data bytes are clocked out rather than one. These protocols
are shown in Figure 1, Figure 2, and Figure 3.
The Command byte is eight bits (one byte) wide. This byte
carries the address of the MIC280 register to be operated
upon. The command byte values corresponding to the vari-
ous MIC280 registers are shown in Table 1. Other command
byte values are reserved, and should not be used.
Slave Address
The MIC280 will only respond to its own unique slave ad-
dress. A match between the MIC280s address and the
address specied in the serial bit stream must be made to
initiate communication. The MIC280s slave address is xed
at the time of manufacture. Eight different slave addresses
are available as determined by the part number. See Table
2 below and the Ordering Information table above.
Part Number
Slave Address
MIC280-0BM6
100 1000
b
= 48
h
MIC280-1BM6
100 1001
b
= 49
h
MIC280-2BM6
100 1010
b
= 4A
h
MIC280-3BM6
100 1011
b
= 4B
h
MIC280-4BM6
100 1100
b
= 4C
h
MIC280-5BM6
100 1101
b
= 4D
h
MIC280-6BM6
100 1110
b
= 4E
h
MIC280-7BM6
100 1111
b
= 4F
h
Table 2: MIC280 Slave Addresses
Alert Response Address
In addition to the Read_Byte, Write_Byte, and Read_Word
protocols, the MIC280 adheres to the SMBus protocol for
response to the Alert Response Address (ARA). The MIC280
expects to be interrogated using the ARA when it has as-
serted its /INT output.
Temperature Data Format
The least-signicant bit of each temperature register (high
bytes) represents one degree Centigrade. The values are in
a twos complement format, wherein the most signicant bit
Command Byte
Power-on
Target Register
Value
Default
Label
Description
Read
Write
TEMP0
Local temperature result
00
h
n/a
00
h
(0癈)
TEMP1h
Remote temperature result, high byte
01
h
n/a
00
h
(0癈)
STATUS
Status
02
h
n/a
00
h
CONFIG
Conguration
03
h
03
h
80
h
IMASK
Interrupt mask register
04
h
04
h
07
h
THIGH0
Local temperature high limit
05
h
05
h
3C
h
(60癈)
TLOW0
Local temperature low limit
06
h
06
h
00
h
(0癈)
THIGH1h
Remote temperature high limit, high byte
07
h
07
h
50
h
(80癈)
TLOW1h
Remote temperature low limit, high byte
08
h
08
h
00
h
(0癈)
LOCK
Security register
09
h
09
h
00
h
TEMP1l
Remote temperature result, low byte
10
h
n/a
00
h
THIGH1l
Remote temperature high limit, low byte
13
h
13
h
00
h
TLOW1l
Remote temperature low limit, low byte
14
h
14
h
00
h
CRIT1
Remote over-temperature limit
19
h
19
h
64
h
(100癈)
CRIT0
Local over-temperature limit
20
h
20
h
46
h
(70癈)
MFG_ID
Manufacturer Identication
FE
h
n/a
2A
h
DEV_ID
Device and revision identication
FF
h
n/a
0x
h
*
* The lower nibble contains the die revision level, e.g., Rev 0 = 00h.
Table 1: MIC280 Register Addresses