L9963E datasheet(29/184 Pages) STMICROELECTRONICS

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4.2.4.2

Burst access

The Burst Access supports only READ commands. It can be used to reduce the time needed to readout long data

series from a single unit. The addressed unit receives the Burst command and starts replying the requested data

frame by frame towards the MCU. Any reply is buffered into L9963E Master unit, which passes it to the MCU on

its next command.

Figure 14. Burst access

1st

MOSI

Dummy Frames (all zeroes)

Last MOSI

1st

MISO

Burst Answer

NCS

SCK

MOSI

MISO

TWAIT

Table 21 describes the burst frame sequence.

•

In case L9963E is configured in SPI mode, its internal buffer will store answers incoming from upper units.

Apply the following strategy to download the burst data:

–

First frame (sent with a single NCS window as a normal command)

◦

First MOSI contains the corresponding Burst command (see Table 23 for available commands)

◦

First MISO stores the answer to the previous MCU command, as per out-of-frame behavior

–

Wait for burst answer to come back to the Master unit

◦

400 μs (in case iso_freq_sel = 11)

◦

3 ms (in case iso_freq_sel = 00)

–

Intermediate frames (all downloaded keeping NCS low)

◦

Intermediate MOSI can be dummy commands (e.g. all zeroes). They are not interpreted by the

L9963E SPI logic

◦

Intermediate MISO contain burst data formatted as in Table 21

–

Last frame (attached to intermediate frames, keeping NCS low)

◦

Last MOSI must be a valid command, because it will be interpreted by L9963E SPI logic

◦

Last MISO contains last burst data register (MISOn) as shown in Table 21

•

In case L9963E transceiver is interposed between MCU and L9963E, refer to the L9963T datasheet. The

Application Information section hosts a paragraph explaining how to handle burst commands.

Table 21. SPI protocol: answer to a burst read request

Dev ID

Command

Unused (Any Data Is Possible)

CRC

Dev ID

Command feedback

DATA READ

CRC

Dev ID

1 1

Frame Num

(00010)

DATA READ

CRC

L9963E

Serial communication interface

DS13636 - Rev 12

page 29/184

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