33784 datasheet(19/30 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33784

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

The response is sent during the next message following a

valid Request Status command to the addressed device.

Because this is a long-word only command, there is no short-

word response.

The I/O bits reflect the logic states of the I/O pins. These

states are latched into an internal register after the Request

Status command is received (approximately TBD

μs after the

bus rises above the frame threshold), and are held until the

response is transmitted. Any activity that occurs on the I/O

pins after the states are latched will be ignored.

Figure 10. Request Status Command and Response Format

REQUEST AN0 COMMAND AND RESPONSE

This command causes the analog voltage on the AN0 pin

to be measured and converted by the on-chip 10-bit ADC.

The approximate timing for the conversion following this

command is shown in Figure 11. The response to this

command depends on the format in which the command was

sent. The sensor data is sent in the format shown in Table 10.

The 33784 will only act on this command if the address bits

in the command match the address that the device was

initialized with. If the addresses do not match, the device will

do nothing and no response will be generated.

Data

Address

Command

Word Type

––––––––

0001

LW & ELW

Not Valid

SW & ESW (8-bit)

Not Valid

ESW (10-bit)

Response

Word Type

00000

BSH BSL

IO2

IO1

IO0

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.

An address value of 0000 is ignored by all devices.

BSH = High Side Bus switch position (1 = closed).

BSL = Low Side Bus switch position (1 = closed).

“–” = Don’t care bit. Can be 0 or 1.

IO[2:0] = Values at logic I/Os.

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