Philips LPC2119 User Manual page 166

Philips Semiconductors
ARM-based Microcontroller
Rx Frame Status Register (CANRFS - 0xE00x x020)
This register defines the characteristics of the current received message. It is read-only in normal operation, but can be written
for testing purposes if the RM bit in CANMOD is 1.
Table 132: CAN Rx Frame Status Register (CANRFS - 0xE00x x020)
CANRFS Name Function
If the BP bit (below) is 0, this value is the zero-based number of the Lookup Table
RAM entry at which the Acceptance Filter matched the received Identifier.
9:0 ID Index Disabled entries in the Standard tables are included in this numbering, but will not
be matched. See the section "Examples of Acceptance Filter Tables and ID Index
Values" on page 175 for examples of ID Index values.
If this bit is 1, the current message was received in AF Bypass mode, and the ID
10 BP
Index field (above) is meaningless.
The field contains the Data Length Code (DLC) field of the current received
message. When RTR=0, this is related to the number of data bytes available in
the CANRDA and CANRDB registers as follows:
19:16 DLC
0000-0111 = 0 to 7 bytes
With RTR=1, this value indicates the number of data bytes requested to be sent
back, with the same encoding.
This bit contains the Remote Transmission Request bit of the current received
message. 0 indicates a Data Frame, in which (if DLC is non-zero) data can be
30 RTR read from the CANRDA and possibly the CANRDB registers. 1 indicates a
Remote frame, in which case the DLC value identifies the number of data bytes
requested to be sent using the same Identifier.
A 0 in this bit indicates that the current received message included an 11-bit
31 FF Identifier, while a 1 indicates a 29-bit Identifier. This affects the contents of the
CANid register described below.
Rx Identifier Register (CANRID - 0xE00x x024)
This register contains the Identifier field of the current received message. It is read-only in normal operation, but can be written
for testing purposes if the RM bit in CANmod is 1. It has two different formats depending on the FF bit in CANRFS.
Table 133: CAN Rx Identifier Register when FF=0 (CANRID - 0xE00x x024)
CANRID Name Function
The 11-bit Identifier field of the current received message. In CAN 2.0A, these bits
10:0 ID
are called ID10-0, while in CAN 2.0B they're called ID29-18.
Table 134: CAN Rx Identifier Register when FF=1 (CANRID - 0xE00x x024)
CANRID Name Function
The 29-bit Identifier field of the current received message. In CAN 2.0B these bits
28:0 ID
are called ID29-0.
CAN Controllers and Acceptance Filter
1000-1111 = 8 bytes
166
Preliminary User Manual
LPC2119/2129/2292/2294
Reset Value RM Set
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Reset Value RM Set
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Reset Value RM Set
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January 08, 2004
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