MCP2510-SLASHST datasheet(51/80 Pages) MICROCHIP

51 / 80 page

DS21291F-page 51

MCP2510

9.0

MODES OF OPERATION

The MCP2510 has five modes of operation. These

modes are:

Configuration Mode.

Normal Mode.

Sleep Mode.

Listen-Only Mode.

Loopback Mode.

The operational mode is selected via the CANCTRL.

REQOP bits (see Register 9-1). When changing

modes, the mode will not actually change until all pend-

ing message transmissions are complete. Because of

this, the user must verify that the device has actually

changed into the requested mode before further oper-

ations are executed. Verification of the current operat-

ing mode is done by reading the CANSTAT. OPMODE

bits (see Register 9-2).

9.1

Configuration Mode

The MCP2510 must be initialized before activation.

This is only possible if the device is in the configuration

mode. Configuration mode is automatically selected

after powerup or a reset, or can be entered from any

other mode by setting the CANTRL.REQOP bits to

‘100’. When configuration mode is entered all error

counters are cleared. Configuration mode is the only

mode where the following registers are modifiable:

• CNF1, CNF2, CNF3

• TXRTSCTRL

• Acceptance Filter Registers

• Acceptance Mask Registers

Only when the CANSTAT.OPMODE bits read as ‘100’

can the initialization be performed, allowing the config-

uration registers, acceptance mask registers, and the

acceptance filter registers to be written. After the con-

figuration is complete, the device can be activated by

programming the CANCTRL.REQOP bits for normal

operation mode (or any other mode).

9.2

Sleep Mode

The MCP2510 has an internal sleep mode that is used

to minimize the current consumption of the device. The

SPI interface remains active even when the MCP2510

is in sleep mode, allowing access to all registers.

To enter sleep mode, the mode request bits are set in

the CANCTRL register. The CANSTAT.OPMODE bits

indicate whether the device successfully entered sleep

mode. These bits should be read after sending the

sleep command to the MCP2510. The MCP2510 is

active and has not yet entered sleep mode until these

bits indicate that sleep mode has been entered. When

in internal sleep mode, the wakeup interrupt is still

active (if enabled). This is done so the MCU can also

be placed into a sleep mode and use the MCP2510 to

wake it up upon detecting activity on the bus.

When in sleep mode, the MCP2510 stops its internal

oscillator. The MCP2510 will wake-up when bus activity

occurs or when the MCU sets, via the SPI interface, the

CANINTF.WAKIF bit to ‘generate’ a wake up attempt

(the CANINTF.WAKIF bit must also be set in order for

the wakeup interrupt to occur). The TXCAN pin will

remain in the recessive state while the MCP2510 is in

sleep mode. Note that Sleep Mode will be entered

immediately, even if a message is currently being

transmitted, so it is necessary to insure that all TXREQ

bits are clear before setting Sleep Mode.

9.2.1

WAKE-UP FUNCTIONS

The device will monitor the RXCAN pin for activity while

it is in sleep mode. If the CANINTE.WAKIE bit is set,

the device will wake up and generate an interrupt.

Since the internal oscillator is shut down when sleep

mode is entered, it will take some amount of time for the

oscillator to start up and the device to enable itself to

receive messages. The device will ignore the message

that caused the wake-up from sleep mode as well as

any messages that occur while the device is ‘waking

up.’ The device will wake up in listen-only mode. The

MCU must set normal mode before the MCP2510 will

be able to communicate on the bus.

The device can be programmed to apply a low-pass fil-

ter function to the RXCAN input line while in internal

sleep mode. This feature can be used to prevent the

device from waking up due to short glitches on the CAN

bus lines. The CNF3.WAKFIL bit enables or disables

the filter.

9.3

Listen Only Mode

Listen-only mode provides a means for the MCP2510

to receive all messages including messages with

errors. This mode can be used for bus monitor applica-

tions or for detecting the baud rate in ‘hot plugging’ sit-

uations. For auto-baud detection it is necessary that

there are at least two other nodes, which are communi-

cating with each other. The baud rate can be detected

empirically by testing different values until valid mes-

sages are received. The listen-only mode is a silent

mode, meaning no messages will be transmitted while

in this state, including error flags or acknowledge sig-

nals. The filters and masks can be used to allow only

particular messages to be loaded into the receive reg-

isters, or the filter masks can be set to all zeros to allow

a message with any identifier to pass. The error

Note:

Care must be exercised to not enter sleep

mode while the MCP2510 is transmitting a

message. If sleep mode is requested while

transmitting, the transmission will stop

without completing and errors will occur on

the bus. Also, the message will remain

pending and transmit upon wake up.

MCP2510-/ST 数据表(PDF) 51 Page - Microchip Technology

MCP2510-/ST 数据表(HTML) 51 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 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

数据表下载