CS5461A datasheet(36/41 Pages) CIRRUS

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CS5461A

DS661F1

8. AUTO-BOOT MODE USING E2PROM

When the CS5461A MODE pin is asserted (logic 1), the

CS5461A auto-boot mode is enabled. In auto-boot

mode, the CS5461A downloads the required com-

mands and register data from an external serial

E2PROM, allowing the CS5461A to begin performing

energy measurements.

8.1 Auto-Boot Configuration

A typical auto-boot serial connection between the

CS5461A and a E2PROM is illustrated in Figure 14. In

auto-boot mode, the CS5461A’s CS and SCLK are con-

figured as outputs. The CS5461A asserts CS, provides

a clock on SCLK, and sends a read command to the

E2PROM on SDO. The CS5461A reads the user-speci-

fied commands and register data presented on the SDI

pin. The E2PROM’s programmed data is utilized by the

CS5461A to change the designated registers’ default

values and begin registering energy.

Figure 14 also shows the external connections that

would be made to a calibrator device, such as a PC or

custom calibration board. When the metering system is

installed, the calibrator would be used to control calibra-

tion and/or to program user-specified commands and

calibration values into the E2PROM. The user-specified

commands/data will determine the CS5461A’s exact

operation, when the auto-boot initialization sequence is

running. Any of the valid commands can be used.

8.2 Auto-Boot Data for E2PROM

Below is an example code set for an auto-boot se-

quence. This code is written into the E2PROM by the us-

er. The serial data for such a sequence is shown below

in single-byte, hexidecimal notation:

- 40 00 00 61

Write Configuration Register, turn high-pass filters

on, set K=1.

- 44 7F C4 A9

Write value of 0x7FC4A9 to Current Gain

- 48 FF B2 53

Write value of 0xFFB253 to Voltage Gain

- 4C 00 7D 00

Set PulseRateE1,2 Register to 1000 Hz.

- 74 00 00 04

Unmask bit #2 (LSD) in the Mask Register).

- E8

Start continuous conversions

- 78 00 01 00

Write STOP bit to Control Register, to terminate

auto-boot initialization sequence.

8.3 Suggested E2PROM Devices

Several industry-standard, serial E2PROMs that will

successfully run auto-boot with the CS5461A are listed

below:

•

Atmel AT25010, AT25020 or AT25040

•

National Semiconductor NM25C040M8 or NM25020M8

•

Xicor X25040SI

These types of serial E2PROMs expect a specific 8-bit

command (00000011) in order to perform a memory

read. The CS5461A has been hardware programmed to

transmit this 8-bit command to the E2PROM at the be-

ginning of the auto-boot sequence.

Figure 14. Typical Interface of E2PROM to CS5461A

CS5461A

EEPROM

EOUT1

EOUT2

MODE

SCLK

SDI

SDO

SCK

Connector to Calibrator

VD+

5 K

Mech. Counter

Stepper Motor

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