Datasheet

Chapter 16 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XE-Family Reference Manual Rev. 1.25
Freescale Semiconductor 639
• The transmission buffer with the lowest local priority field wins the prioritization.
In cases of more than one buffer having the same lowest priority, the message buffer with the lower index
number wins.
16.3.3.5 Time Stamp Register (TSRH–TSRL)
If the TIME bit is enabled, the MSCAN will write a time stamp to the respective registers in the active
transmit or receive buffer right after the EOF of a valid message on the CAN bus (see Section 16.3.2.1,
“MSCAN Control Register 0 (CANCTL0)”). In case of a transmission, the CPU can only read the time
stamp after the respective transmit buffer has been flagged empty.
The timer value, which is used for stamping, is taken from a free running internal CAN bit clock. A timer
overrun is not indicated by the MSCAN. The timer is reset (all bits set to 0) during initialization mode. The
CPU can only read the time stamp registers.
Module Base + 0x00XD Access: User read/write
(1)
1. Read: Anytime when TXEx flag is set (see Section 16.3.2.7, “MSCAN Transmitter Flag Register (CANTFLG)”) and the
corresponding transmit buffer is selected in CANTBSEL (see Section 16.3.2.11, “MSCAN Transmit Buffer Selection Register
(CANTBSEL)”)
Write: Anytime when TXEx flag is set (see Section 16.3.2.7, “MSCAN Transmitter Flag Register (CANTFLG)”) and the
corresponding transmit buffer is selected in CANTBSEL (see Section 16.3.2.11, “MSCAN Transmit Buffer Selection Register
(CANTBSEL)”)
76543210
R
PRIO7 PRIO6 PRIO5 PRIO4 PRIO3 PRIO2 PRIO1 PRIO0
W
Reset: 00000000
Figure 16-36. Transmit Buffer Priority Register (TBPR)
Module Base + 0x00XE Access: User read/write
(1)
1. Read: For transmit buffers: Anytime when TXEx flag is set (see Section 16.3.2.7, “MSCAN Transmitter Flag Register
(CANTFLG)”) and the corresponding transmit buffer is selected in CANTBSEL (see Section 16.3.2.11, “MSCAN Transmit
Buffer Selection Register (CANTBSEL)”). For receive buffers: Anytime when RXF is set.
Write: Unimplemented
76543210
R TSR15 TSR14 TSR13 TSR12 TSR11 TSR10 TSR9 TSR8
W
Reset: xxxxxxxx
Figure 16-37. Time Stamp Register — High Byte (TSRH)