COMMELL MPX-2515 - Manual (Page 6)

Commell MPX-2515 User’s Guide Rev 0100
Taiwan Commate Computer Inc. 6
Bit 4 TXEP: Transmit Error-Passive flag bit.
Bit 3 RXEP: Receive Error-Passive flag bit.
Bit 2 TXWAR: Transmit Error Warning flag bit.
Bit 1 RXWAR: Receive Error Warning flag bit.
Bit 0 EWARN: Error Warning flag bit.
3 1 Firmware Message Buffer (FMB) status:
Bit 7:6:5:4:3 Buffer 2 Overwritten Number
This number increases by value of one if a CAN message
has arrived and has overwritten at Buffer 2 storage prior to
the previous stored has read back by the USB host.
Bit 2 Buffer 2 Indicator
0 / 1: empty / occupied
Bit 1 Buffer 1 Indicator
0 / 1: empty / occupied
Bit 0 Buffer 0 Indicator
0 / 1: empty / occupied
4 1 Reserved.
5 1 Reserved.
6 1 Reserved.
7 1 Reserved.
Table 1 Status Packet Format
1.3 Request Packet vs. Response Packet
This section defines the format of Request Packet as well as the format of Response
Packet. At this moment, both Request Packets and Response Packets are limited to
64 bytes per packet.
The Request Packet is used to send command to the CY8C24794 micro controller
in the MPX-2515 CAN USB Card to carry out over the connecting CAN bus. A
Request Packet is sent to endpoint 2 of the MPX-2515 card through a BULK OUT
transfer.
While, the Response Packet is used to retrieve the result of an executed command
from the CY8C24794 micro controller. A Response Packet is returned from
endpoint 1 of the MPX-2515 card through a BULK IN transfer.
The following table defines the Request Packet used in CCA-P.
OFFSET NAME DESCRIPTION
0 HEADER_MSB 0X55
1 HEADER_LSB 0XAA
2 VERSION 0X01
3 SIZEOF_DATA The number of bytes residing in the DATA field.