MCP6S92 datasheet(22/40 Pages) MICROCHIP

22 / 40 page

 2004 Microchip Technology Inc.

DS21908A-page 22

MCP6S91/2/3

5.2

Registers

The analog functions are programmed through the SPI

interface using 16-bit words (see Figure 5-1 and

Figure 5-2). This data is sent to two of three 8-bit regis-

ters: Instruction register (Register 5-1), Gain register

(Register 5-2) and Channel register (Register 5-3).

There are no power-up defaults for these three

registers.

5.2.1

ENSURING VALID DATA IN THE

REGISTERS

After power up, the registers contain random data that

must be initialized. Sending valid gain and channel

selection commands to the internal registers puts valid

data into those registers. Also, the internal state

machine starts in an arbitrary state. Toggling the Chip

Select pin (CS) from high to low, then back to high

again, puts the internal state machine in a known, valid

condition (this can be done by entering any valid

command).

After power-up, and when the power supply voltage

dips below the minimum valid VDD (VDD_VAL), the inter-

nal register data and state machine may need to be

reset. This is accomplished as described before. Use

an external system supervisor to detect these events

so that the microcontroller will reset the PGA state and

registers.

A 0.1 µF bypass capacitor mounted as close as

possible to the VDD pin provides additional transient

immunity.

5.2.2

INSTRUCTION REGISTER

The Instruction register has 3 command bits and 1 indi-

rect address bit; see Register 5-1. The command bits

include a NOP (000) to support daisy-chaining (see

Section 5.3 “Daisy-Chain Configuration”); the other

NOP

commands shown should not be used (they are

reserved for future use). The device is brought out of

Shutdown mode when a valid command, other than

NOP

or Shutdown, is sent and CS is raised.

INSTRUCTION REGISTER

W-0

U-x

W-0

—

—A0

bit 7

bit 0

bit 7-5

M2-M0: Command bits

000

NOP

(Note 1)

001

PGA enters Shutdown mode as soon as a full 16-bit word is sent and CS is raised.

(Notes 1 and 2)

010

Write to register.

011

NOP

(reserved for future use) (Note 1)

1XX

NOP

(reserved for future use) (Note 1)

bit 4-1

Unimplemented: Read as ‘0’ (reserved for future use)

bit 0

A0: Indirect Address bit

= Addresses the Channel register

= Addresses the Gain register

Note 1:

All other bits in the 16-bit word (including A0) are “don’t cares.”

The device exits Shutdown mode when a valid command (other than NOP or

Shutdown) is sent and CS is raised; that valid command will be executed.

Shutdown does not toggle.

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

MCP6S92 датащи(PDF) 22 Page - Microchip Technology

MCP6S92 датащи(HTML) 22 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

датащи скачать

ссылки URL