GS12281 datasheet(53/97 Pages) SEMTECH

53 / 97 page

GS12281

Final Data Sheet

Rev.9

PDS-061385

February 2019

53 of 97

Semtech

Proprietary & Confidential

www.semtech.com

Note: tcmd_GSPI_conf delay must be observed after every write that modifies

CONTROL_REG.

All connected devices receive this command (by default the Unit Address of all devices

is 0), and the Loop-Through operation will be re-established for all connected devices.

Once configured, each device will only respond to Command Words with a



UNIT ADDRESS field matching the DEV_UNIT_ADDRESS in CONTROL_REG.

Note: Although the Loop-Through and Bus-Through configurations are compatible

with previous generation GSPI enabled devices (backward compatibility), only devices

supporting Unit Addressing can share a chip select. All devices on any single chip select

must be connected in a contiguous chain with only the last device's SDOUT connected

to the application host processor. Multiple chains configured in Bus-Through mode can

have their final SDOUT outputs connected to a single application host processor input.

4.9.10 Default GSPI Operation

By default at power up or after a device reset, the GS12281 is set for Loop-Through

Operation and the internal DEV_UNIT_ADDRESS field of the device is set to 0.

Figure 4-26 shows a functional block diagram of the Configuration and Status Register

(CSR) map in the GS12281.

Figure 4-26: Internal Register Map Functional Block Diagram

The steps required for the application host processor to write to the Configuration and

Status Registers via the GSPI, are as follows:

1. Set Command Word 1 for write access (R/W = 0); set Auto Increment; set the Unit

Address field in the Command Word 1 to match the configured

DEV_UNIT_ADDRESS which will be zero after power-up. Set the Register Address

bits in Command Word 1 to match the upper 7 bits of the register address to be

accessed. Set the bits in Command Word 2 to match the lower 16 bits of the register

address to be accessed. Write Command Word 1 and Command Word 2.

2. Write the Data Word to be written to the first register.

Reg 0

Compare

Configuration and Status Registers

Read/Write

Data to be written / Read Data

DATA

[15:0]

DEV_UNIT_ADDRESS

GSPI_LINK

_DISABLE

GSPI_BUS_

THROUGH

_ENABLE

RESERVED

bits

[4:0]

[13]

[14]

[15]

bits

RESERVED

[12:5]

Lower 16 bits of Register Address

COMMAND 2

[15:0]

bits

[12]

[6:0]

COMMAND 1

At power-up or after a device reset, DEV_UNIT_ADDRESS = 00

[11:7]

[13]

[14]

bits

Upper 7 bits

R/W

Unit Address

32 devices

BCAST

ALL

Auto

Inc

EMEM

[15]

GS12281 Datasheet(PDF) 53 Page - Semtech Corporation

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