ADBMS2950BCCSZ datasheet(22/97 Pages) AD

22 / 97 page

ADBMS2950B

Data Sheet

Rev. 0 | Page 22 of 97

NETWORK LAYER OF (ISO)SPI PROTOCOL

This chapter describes the communication protocol of the SPI

(Port A) or isoSPI (Port A or Port B) peripheral interface.

Communication Protocol

The protocol formats for commands are shown from Table 25

to Table 29. Table 24 shows the protocol keys to read the

protocol diagrams.

Table 24. Protocol Keys

Name

Description

CMD0

Command Byte 0 (see Table 29).

CMD1

Command Byte 1 (see Table 29).

PEC0

Packet Error Code Byte 0 (see Table 30).

PEC1

Packet Error Code Byte 1 (see Table 30).

DPEC0

Data Packet Error Code Byte 0 (see Table 31 and Table 32).

DPEC1

Data Packet Error Code Byte 1 (see Table 31 and Table 32).

...

Continuation of Protocol.

B0 to B3

1st four bytes of SPI transaction received by all devices in daisy-

chain.

S<m>:B<n>

Byte n send to (WRITE) or read from (READ) device m.

Total number of devices in daisy-chain.

Table 25. WRITE Command. Data and DPEC Bytes are Sent from Serial Controller to Peripheral

SN:B0

...

SN:B5

SN:B6

SN:B7

...

S1:B0

...

S1:B5

S1:B6

S1:B7

CMD0

CMD1

PEC0

PEC1

Data Byte 0

...

Data Byte 5

DPEC0

DPEC1

...

Data Byte 0

...

Data Byte 5

DPEC0

DPEC1

Table 26. Read Command. Data and DPEC Bytes are Sent from Serial Peripheral to Controller

S1:B0

...

S1:B5

S1:B6

S1:B7

...

SN:B0

...

SN:B5

SN:B6

SN:B7

CMD0

CMD1

PEC0

PEC1

Data Byte 0

...

Data Byte 5

DPEC0

DPEC1

...

Data Byte 0

...

Data Byte 5

DPEC0

DPEC1

Table 27. Read-All Command

S1:B0

S1:B1

...

S1:B19

S1:B20

S1:B21

CMD0

CMD1

PEC0

PEC1

Data Byte 0

Data Byte 1

...

Data Byte 19

DPEC0

DPEC1

Table 28. Poll or 4-Byte-Only Commands. The Optional Poll Data is Sent from Peripheral to Controller

...

CMD0

CMD1

PEC0

PEC1

Optional Poll Data

...

Table 29. Command Format

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

CMD0

CC[10]

CC[9]

CC[8]

CMD1

CC[7]

CC[6]

CC[5]

CC[4]

CC[3]

CC[2]

CC[1]

CC[0]

For most read and write commands, the data is 6 register bytes

plus 6 bits of command counter, which are part of the DPEC0

byte for a total of 54 data bits followed by the PEC10 bits.

Without the command counter bits, this makes 48 register data

bits, which is why those commands are indicated by the RD48

or WR48 command type throughout this data sheet.

The special Read All (RDALL...) commands RDALLI,

RDALLA, RDALLV, RDALLR, RDALLX, and RDALLC return

20 bytes of register data plus command counter followed by the

PEC10 bits as shown in Table 27.

The RDALL commands do not return any data received at the

ADBMS2950B's isoSPI controller port, thus can be used to read

data from a single device only, which can be a single IC

application as shown in Figure 19 or reading data from the first

ADBMS2950B shown in Figure 20, Figure 21, or Figure 22.

The limit to one device or the first device in a daisy-chain is

indicated in Table 27 by showing S1:... bytes only.

Table 32 shows the format for the DPEC containing command

counter and PEC10 when reading data.

For write commands, register data is sent to ADBMS2950B,

followed by the DPEC. For example, when writing CFGA

CFGA5, DPEC0, and DPEC1. Table 31 shows the format for

DPEC when writing data.

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