33784 datasheet(24/30 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33784

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

Figure 17. Format Control Command and Response Format

FORMAT CONTROL REGISTERS

The enhanced DSI Register locations are shown in

Figure 9. The ADDR bits in the Format Control Command

select the Format Control Register to which data is written or

from which data is read. The data is 4 bits.

Table 9. Format Control Registers

CRC POLYNOMIAL

The CRC Taps control the feedback for the CRC

Polynomial. The MSB represents the X3 bit. The LSB

represents X0 or the value 1 if set or 0 if not set. The standard

DSI CRC of X4+1 would be obtained by loading 0001 into the

Format register 0. The X4 pin is always considered on, so

nothing has to be done for it. On a reset or clear, the standard

DSI CRC taps are loaded into these registers.

SEED

The Seed is the starting value loaded into the CRC

checking registers before each transaction starts. The default

DSI seed of 1010 would be selected by loading 1010 into

control register 2. On reset or clear, the standard DSI seed is

loaded into this register.

SHORT-WORD DATA LENGTH

The Short-Word Data Length controls the number of bits of

data in a short word. This can be set to 8 or 10. On a reset or

clear, the value in this register defaults to 8. If a number other

than 8 or 10 is written to the register, it is ignored and the

contents of the register are not changed. The standard DSI

short-word data length would be set by loading 1000 into this

FORMAT SELECTION

The Format selection determines whether the standard

DSI values will be used or the values in the Format register.

The switch to the values in the format registers occurs when

1111 is successfully written to control register 7 in a single

command. If the register is currently cleared, and one of the

data bits is not received as a logic [1], the data in the register

will remain all zeroes and the device will not use the Format

when a ‘0000’ is successfully written to control register 7. If

the registers bits are all set, and one of the bits is received as

a logic [1], the value of the bits in the register will remain 1111

and the switch back to Standard DSI values will not occur.

This is done to reduce the possibility of switching operation

modes due to a corrupted command. When using the Format

this register back to 0000, will be ignored.

Data

Address

Command

Word Type

R/W

ADD

Data

1010

LW & ELW

Not Valid

SW & ESW (8-bit)

Not Valid

ESW (10-bit)

Response

Word Type

0000

R/W

ADD

DAT

LW & ELW

No Response

SW & ESW (8-bit)

No Response

ESW (10-bit)

Legend

A[3:0] = Address bits. The address of the selected device.

R/W = Controls if this is a read or write. Write = 1.

ADDR[2:0] = Pointer to Format control register which is to be accessed.

DATA[3:0] = Data to read from or write to in the pointed to Format

Control Register.

Format Control

Description

CRC Polynomial

Reserved

Seed

Reserved

Short-Word Data Length

Reserved

Format Selection

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