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DS21Q55

28. EXTENDED SYSTEM INFORMATION BUS (ESIB)

The ESIB allows two DS21Q55s to share an 8-bit CPU bus for the purpose of reporting alarms and interrupt status as a group. With a single bus read, the host can be updated with alarm or interrupt status from all members of the group. There are two control registers, ESIBCR1 and ESIBCR2, and four information registers, ESIB1, ESIB2, ESIB3, and ESIB4. As an example, eight DS21Q55s can be grouped into an ESIB group. A single read of the ESIB1 register of ANY member of the group will yield the interrupt status of all eight DS21Q55s. Therefore the host can determine which device or devices are causing an interrupt without polling all eight devices. Via ESIB2 the host can gather synchronization status on all members of the group. ESIB3 and ESIB4 can be programmed to report various alarms on a device by device basis.

There are three device pins involved in forming a ESIB group. These are ESIBS0, ESIBS1, and ESIBRD. A 10k pullup resistor must be provided on ESIBS0, ESIBS1, and ESIBRD.

ESIB GROUP OF FOUR DS21Q55s Figure 30-1

VDD

10k (3)

DS21Q55 # 1

CPU I/F

ESIB0

ESIB1

 

 

ESIBRD

DS21Q55 # 2

CPU I/F

ESIB0

ESIB1

 

ESIBRD

DS21Q55 # 3

ESIB0

CPU I/F

ESIB1

 

 

ESIBRD

DS21Q55 # 4

ESIB0

CPU I/F

ESIB1

 

 

ESIBRD

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information.

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Maxim specifications Extended System Information BUS Esib, Esib Group of Four DS21Q55s Figure