PCA9541 データシートの表示（PDF） - Philips Electronics
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PCA9541 Datasheet PDF : 30 Pages
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Philips Semiconductors
2-to-1 I2C master selector with interrupt logic and reset
Product data sheet
PCA9541
Table 7 describes which command needs to be written to the Control
Register when a master device wants to take control of the I2C-bus.
Byte written to the Control Register is a function of the current
I2C-bus control status performed after an initial reading of the
Control Register.
Current status of the I2C-bus is determined by the bits MYBUS,
NMYBUS, BUSON and NBUSON is one of the following:
– The master reading its Control Register does not have control and
the I2C-bus is off.
– The master reading its Control Register does not have control and
the I2C-bus is on.
– The master reading its Control Register has control and the
I2C-bus is off.
– The master reading its Control Register has control and the
I2C-bus is on.
‘I2C-bus off’ means that upstream and downstream channels are not
connected together.
‘I2C-bus on’ means that upstream and downstream channels are
connected together.
Remark: Only the 4 LSBs of the Control Register are described in
Table 7 since only those bits control the I2C-bus control. The logic
value for the 4 MSBs is specific to the application and are not
discussed in the table.
The Read sequence is performed by the master as following:
S — 111xxxx0 — 000x0001 — Sr — 111xxxx1 — DataRead — P
The Write sequence is performed by the master as following:
S — 111xxxx0 — 000x0001 — DataWritten — P
Table 7. Bus control sequence
Read Control Register performed by the Master
Byte Read
only the
4 LSBs
are shown
Status
NBUSON BUSON NMYBUS
Hex
0x0
Bus off Has control
0
0
0
0x1
Bus off No control
0
0
0
0x2
Bus off No control
0
0
1
0x3
Bus off Has control
0
0
1
0x4
Bus on Has control
0
1
0
0x5
Bus on No control
0
1
0
0x6
Bus on No control
0
1
1
0x7
Bus on Has control
0
1
1
0x8
Bus on Has control
1
0
0
0x9
Bus on No control
1
0
0
0xA
Bus on No control
1
0
1
0xB
Bus on Has control
1
0
1
0xC
Bus off Has control
1
1
0
0xD
Bus off No control
1
1
0
0xE
Bus off No control
1
1
1
0xF
Bus off Has control
1
1
1
NOTES:
1. x0x0 = 0x0, 0x2, 0x8, 0xA
x0x1 = 0x1, 0x3, 0x9, 0xB
x1x0 = 0x4, 0x6, 0xC, 0xE
x1x1 = 0x5, 0x7, 0xD, 0xF
MYBUS
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Write Control Register performed by the Master
Byte Written
only the 4 LSBs are shown
(see Note 1)
Action performed
to take Mastership
Binary
Hex
x1x0
0x4 Bus on
x1x0
0x4 Bus on, Take control
x1x1
0x5 Bus on, Take control
x1x1
0x5 Bus on
No write required
–
No change
x1x0
0x4 Take control
x1x1
0x5 Take control
No write required
–
No change
No write required
–
No change
x0x0
0x0 Take control
x0x1
0x1 Take control
No write required
–
No change
x0x0
0x0 Bus on
x0x0
0x0 Bus on, Take control
x0x1
0x1 Bus on, Take control
x0x1
0x1 Bus on
2004 Oct 01
10
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