MCP25020ISLASHP datasheet(42/66 Pages) MICROCHIP

42 / 66 page

MCP2502X/5X

DS21664D-page 42

7.3.2

CONVERSION-ON-REQUEST

MODE

If the Conversion-on-request mode is selected, the

device performs an A/D conversion only after receiving

a Read A/D Registers or Read Register Receive

message (IRM). In the case of the Read A/D Registers

command, all of the GPIO pins that have been

configured as analog input channels will have an A/D

conversion done before the data frame is sent. When a

Read Register Receive message is initiated (extended

message format only), the A/D conversion is performed

when the MSB of the analog channel is requested, with

the MSB result being transferred. A subsequent read of

the LSB will transmit the value latched when the MSB

was requested (it is recommended that the Read A/D

Registers receive message is used to obtain complete

analog channel values in one message).

7.4

A/D Threshold Detection

Once an A/D auto-conversion has been completed, the

A/D channel result(s) can be compared to a value

stored in the associated A/D channel comparator

registers.

If the value in the analog channel result registers (i.e.,

AN0L and AN10H registers for analog channel 0) is

lower or higher than the value in the A/D comparator

registers (as specified by a corresponding polarity bit),

a transmit-on-change message will be sent (TXID2).

The

threshold-detection

function

for

all

analog

channels is bit-selectable.

If the A/D channel has been configured for transmit-on-

change mode, the MCP2505 will send a transmit

message with the appropriate data. It is possible that

more than one A/D channel has a change-of-state

condition. This does not pose a problem since all

analog channel data is provided in the transmit

message.

A/D MODULE RESULT REGISTER MSB (ADRESNH)

A/D MODULE RESULT REGISTER LSB (ADRESNL)

R-x

AD9

AD8

AD7

AD6

AD5

AD4

AD3

AD2

bit 7

bit 0

bit 7-0

AD9:AD2: Most Significant A/D Result bits

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

R-x

U-0

AD1

AD0

—

bit 7

bit 0

bit 7-6

AD1:AD0: Least significant A/D Result bits

bit 5-0

Unimplemented: Reads as ‘0’

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

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