Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XHY-Family Reference Manual Rev. 1.01
Freescale Semiconductor
375
•
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.
11.3.3.5
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 11.3.2.1,
“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 11.3.2.7, “MSCAN Transmitter Flag Register (CANTFLG)
”) and the
corresponding transmit buffer is selected in CANTBSEL (see
Section 11.3.2.11, “MSCAN Transmit Buffer Selection Register
(CANTBSEL)
”)
Write: Anytime when TXEx flag is set (see
Section 11.3.2.7, “MSCAN Transmitter Flag Register (CANTFLG)
”) and the
corresponding transmit buffer is selected in CANTBSEL (see
Section 11.3.2.11, “MSCAN Transmit Buffer Selection Register
(CANTBSEL)
”)
7
6
5
4
3
2
1
0
R
PRIO7
PRIO6
PRIO5
PRIO4
PRIO3
PRIO2
PRIO1
PRIO0
W
Reset:
0
0
0
0
0
0
0
0
Figure 11-36. Transmit Buffer Priority Register (TBPR)
Module Base + 0x00XE
Access: User read/write
(1)
1. Read: Anytime when TXEx flag is set (see
Section 11.3.2.7, “MSCAN Transmitter Flag Register (CANTFLG)
”) and the
corresponding transmit buffer is selected in CANTBSEL (see
Section 11.3.2.11, “MSCAN Transmit Buffer Selection Register
(CANTBSEL)
”)
Write: Unimplemented
7
6
5
4
3
2
1
0
R
TSR15
TSR14
TSR13
TSR12
TSR11
TSR10
TSR9
TSR8
W
Reset:
x
x
x
x
x
x
x
x
Figure 11-37. Time Stamp Register — High Byte (TSRH)
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