Introduction
isoSPI is a proprietary Linear Technology protocol that uses Isolated Transceivers to provide robust galvanic isolation for various digital serial communication interfaces and devices. Isolation barriers are implemented using either inexpensive Ethernet transformers, coupling capacitors or embedded inductors. The main benefit is very low EMI susceptibility and emissions, as well as high noise immunity, to preserve signal integrity.
Architecture
| Maximum Clock Speed | 1MHz (see p.12 in LTC6820 datasheet) |
|---|---|
| Synchronous/Asynchronous | Synchronous |
| Lines | 2 (twisted pair) |
| Number of Slaves | Limited by the number of transceivers |
| Communication Direction | Bidirectional (Full-Duplex) |
Scope Captures
Being able to decode scope captures are pretty useful when debugging.
(Taken from Table 1 in the LTC6820 datasheet)
| Pulse Type | First Level | Second Level | Ending Level |
|---|---|---|---|
| Long +1 | +Va (150ns) | -Va (150ns) | 0V |
| Long -1 | -Va (150ns) | +Va (150ns) | 0V |
| Short +1 | +Va (50ns) | -Va (50ns) | 0V |
| Short -1 | -Va (50ns) | +Va (50ns) | 0V |
(Taken from Table 2 in the LTC6820 datasheet)
| SPI Master Event | Transmitted Pulse |
|---|---|
| CS Rising | Long +1 |
| CS Falling | Long –1 |
| SCK Latching Edge, MOSI = 1 | Short +1 |
| SCK Latching Edge, MOSI = 0 | Short –1 |