MCP2510-EST datasheet(52/76 Pages) MICROCHIP

52 / 76 page

MCP2510

DS21291C-page 52

Preliminary

 2000 Microchip Technology Inc.

9.4

Loopback Mode

This mode will allow internal transmission of messages

from the transmit buffers to the receive buffers without

actually transmitting messages on the CAN bus. This

mode can be used in system development and testing.

In this mode the ACK bit is ignored and the device will

allow incoming messages from itself just as if they were

coming from another node. The loopback mode is a

silent mode, meaning no messages will be transmitted

while in this state, including error flags or acknowledge

signals. The TXCAN pin will be in a reccessive state

while the device is in this mode. The filters and masks

can be used to allow only particular messages to be

loaded into the receive registers. The masks can be set

to all zeros to provide a mode that accepts all mes-

sages. The loopback mode is activated by setting the

mode request bits in the CANCTRL register.

9.5

Normal Mode

This is the standard operating mode of the MCP2510.

In this mode the device actively monitors all bus mes-

sages and generates acknowledge bits, error frames,

etc. This is also the only mode in which the MCP2510

will transmit messages over the CAN bus.

CANCTRL - CAN Control Register (ADDRESS: xFh)

R/W-1

R/W-0

U-0

R/W-1

REQOP2 REQOP1 REQOP0

ABAT

—

CLKEN CLKPRE1CLKPRE0

R = Readable bit

W = Writable bit

C = Bit can be cleared by

MCU but not set

U = Unimplemented -

reads as ‘0’

- n = Value at POR reset

bit 7

bit 0

bit 7-5:

REQOP<2:0>: Request Operation Mode

000 = Set Normal Operation Mode

001 = Set Sleep Mode

010 = Set Loopback Mode

011 = Set Listen Only Mode

100 = Set Configuration Mode

All other values for REQOP bits are invalid and should not be used

bit 4:

ABAT: Abort All Pending Transmissions

1 = Request abort of all pending transmit buffers

0 = Terminate request to abort all transmissions

bit 3:

Unimplemented: Reads as ‘0’

bit 2:

CLKEN: CLKOUT Pin Enable

0 = CLKOUT pin disabled (Pin is in high impedance state)

1 =CLKOUT pin enabled

bit 1-0:

CLKPRE<1:0>: CLKOUT Pin Prescaler

00 = FCLKOUT = System Clock/1

01 = FCLKOUT = System Clock/2

10 = FCLKOUT = System Clock/4

11 = FCLKOUT = System Clock/8

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