 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
MCP2510-ISO Datasheet(PDF) 21 Page - Microchip Technology |
|
||||||||||||||||||||||||||||||
MCP2510-ISO Datasheet(HTML) 21 Page - Microchip Technology |
|
|
21 / 80 page  © 2007 Microchip Technology Inc. DS21291F-page 21 MCP2510 4.0 MESSAGE RECEPTION 4.1 Receive Message Buffering The MCP2510 includes two full receive buffers with multiple acceptance filters for each. There is also a separate Message Assembly Buffer (MAB) which acts as a third receive buffer (see Figure 4-1). 4.2 Receive Buffers Of the three Receive Buffers, the MAB is always com- mitted to receiving the next message from the bus. The remaining two receive buffers are called RXB0 and RXB1 and can receive a complete message from the protocol engine. The MCU can access one buffer while the other buffer is available for message reception or holding a previously received message. The MAB assembles all messages received. These messages will be transferred to the RXBN buffers (See Register 4-4 to Register 4-9) only if the acceptance fil- ter criteria are met. When a message is moved into either of the receive buffers the appropriate CANINTF.RXNIF bit is set. This bit must be cleared by the MCU, when it has completed processing the message in the buffer, in order to allow a new message to be received into the buffer. This bit provides a positive lockout to ensure that the MCU has finished with the message before the MCP2510 attempts to load a new message into the receive buffer. If the CANINTE.RXNIE bit is set an interrupt will be gen- erated on the INT pin to indicate that a valid message has been received. 4.3 Receive Priority RXB0 is the higher priority buffer and has two message acceptance filters associated with it. RXB1 is the lower priority buffer and has four acceptance filters associ- ated with it. The lower number of acceptance filters makes the match on RXB0 more restrictive and implies a higher priority for that buffer. Additionally, the RXB0CTRL register can be configured such that if RXB0 contains a valid message, and another valid message is received, an overflow error will not occur and the new message will be moved into RXB1 regard- less of the acceptance criteria of RXB1. There are also two programmable acceptance filter masks available, one for each receive buffer (see Section 4.5). When a message is received, bits <3:0> of the RXBNC- TRL Register will indicate the acceptance filter number that enabled reception, and whether the received mes- sage is a remote transfer request. The RXBNCTRL.RXM bits set special receive modes. Normally, these bits are set to 00 to enable reception of all valid messages as determined by the appropriate acceptance filters. In this case, the determination of whether or not to receive standard or extended mes- sages is determined by the RFXNSIDL.EXIDE bit in the acceptance filter register. If the RXBNCTRL.RXM bits are set to 01 or 10, the receiver will accept only mes- sages with standard or extended identifiers respec- tively. If an acceptance filter has the RFXNSIDL.EXIDE bit set such that it does not correspond with the RXBNCTRL.RXM mode, that acceptance filter is ren- dered useless. These two modes of RXBNCTRL.RXM bits can be used in systems where it is known that only standard or extended messages will be on the bus. If the RXBNCTRL.RXM bits are set to 11, the buffer will receive all messages regardless of the values of the acceptance filters. Also, if a message has an error before the end of frame, that portion of the message assembled in the MAB before the error frame will be loaded into the buffer. This mode has some value in debugging a CAN system and would not be used in an actual system environment. 4.4 RX0BF and RX1BF Pins In addition to the INT pin which provides an interrupt signal to the MCU for many different conditions, the receive buffer full pins (RX0BF and RX1BF) can be used to indicate that a valid message has been loaded into RXB0 or RXB1, respectively. The RXBNBF full pins can be configured to act as buffer full interrupt pins or as standard digital outputs. Config- uration and status of these pins is available via the BFPCTRL register (Register 4-3). When set to operate in interrupt mode (by setting BFPCTRL.BxBFE and BFPCTRL.BxBFM bits to a 1), these pins are active low and are mapped to the CANINTF.RXNIF bit for each receive buffer. When this bit goes high for one of the receive buffers, indicating that a valid message has been loaded into the buffer, the corresponding RXNBF pin will go low. When the CANINTF.RXNIF bit is cleared by the MCU, then the corresponding interrupt pin will go to the logic high state until the next message is loaded into the receive buffer. When used as digital outputs, the BFPCTRL.BxBFM bits must be cleared to a ‘0’ and BFPCTRL.BxBFE bits must be set to a ‘1’ for the associated buffer. In this mode the state of the pin is controlled by the BFPC- TRL.BxBFS bits. Writting a ‘1’ to the BxBFS bit will cause a high level to be driven on the assicated buffer full pin, and a ‘0’ will cause the pin to drive low. When using the pins in this mode the state of the pin should be modified only by using the Bit Modify SPI command to prevent glitches from occuring on either of the buffer full pins. Note: The entire contents of the MAB is moved into the receive buffer once a message is accepted. This means that regardless of the type of identifier (standard or extended) and the number of data bytes received, the entire receive buffer is overwritten with the MAB contents. Therefore the contents of all registers in the buffer must be assumed to have been modified when any message is received. |
Similar Part No. - MCP2510-ISO |
|
Similar Description - MCP2510-ISO |
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.NET |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
