NEC MuPD70F3187, Руководство пользователя

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Chapter 18 AFCAN Controller
User’s Manual U16580EE3V1UD00
Figure 18-31: Transmit history list
18.10.3 Automatic block transmission (ABT)
The automatic block transmission (ABT) function is used to transmit two or more data frames succes-
sively with no CPU interaction. The maximum number of transmit message buffers assigned to the ABT
function is eight (message buffer numbers 0 to 7).
By setting the OPMODE[2:0] bits of the CnCTRL register to 010B, “normal operation mode with auto-
matic block transmission function” (hereafter referred to as ABT mode) can be selected.
To issue an ABT transmission request, define the message buffers by software first. Set the MA0 bit (1)
in all the message buffers used for ABT, and define all the buffers as transmit message buffers by set-
ting the MA[2:0] bits to 000B. Be sure to set the same ID for the message buffers for ABT even when
that ID is being used for all the message buffers. To use two or more IDs, set the ID of each message
buffer by using the CnMIDLm and CnMIDHm registers. Set the CnMDLCm and CnMDATA0m to
CnMDATA7m registers before issuing a transmission request for the ABT function.
After initialization of message buffers for ABT is finished, the RDY bit needs to be set (1). In the ABT
mode, the TRQ bit does not have to be manipulated by software.
After the data for the ABT message buffers has been prepared, set the ABTTRG bit to 1. Automatic
block transmission is then started. When ABT is started, the TRQ bit in the first message buffer (mes-
sage buffer 0) is automatically set to 1. After transmission of the data of message buffer 0 is finished,
the TRQ bit of the next message buffer, message buffer 1, is set automatically. In this way, transmission
is executed successively.
A delay time can be inserted by program in the interval in which the transmission request (TRQ) is auto-
matically set while successive transmission is being executed. The delay time to be inserted is defined
by the CnGMABTD register. The unit of the delay time is DBT (data bit time). DBT depends on the set-
ting of the CnBRP and CnBTR registers.
Among transmit objects within the ABT-area, the priority of the transmission ID is not evaluated. The
data of message buffers 0 to 7 are sequentially transmitted. When transmission of the data frame from
message buffer 7 has been completed, the ABTTRG bit is automatically cleared to 0 and the ABT oper-
ation is finished.
If the RDY bit of an ABT message buffer is cleared during ABT, no data frame is transmitted from that
buffer, ABT is stopped, and the ABTTRG bit is cleared. After that, transmission can be resumed from
1
2
3
4
5
6
7
Tr a n s mit hi s tory li s t(THL)
1
2
3
4
5
6
7
1
2
3
4
5
6
7
1
2
3
4
5
6
7
Event:
- me
ssa ge bu ffer 8 , 5, 6 a nd 10 complete s tr a n s mi ss ion
- THL i s f u ll
- TOVF i s s et
0
0 0
0
L as t o u t-me ssa ge
pointer(LOPT)
Me ssa ge bu ffer 7
Me ssa ge bu ffer 2
Me ssa ge bu ffer 9
Me ssa ge bu ffer 6
Tr a n s mit hi s tory li s t
get pointer(TGPT)
Tr a n s mit hi s tory li s t(THL)
Me ssa ge bu ffer 4
Me ssa ge bu ffer 3
Me ssa ge bu ffer 7
Tr a n s mit hi s tory li s t
get pointer(TGPT)
Tr a n s mit hi s tory li s t(THL)
Tr a n s mit hi s tory li s t
get pointer(TGPT)
L as t o u t-me ssa ge
pointer(LOPT)
TOVF = 1
LOPT i
s b locked
Tr a n s mit
hi s tory
li s t get
pointer
(TGPT)
Tr a n s mit hi s tory li s t(THL)
L as t o u t-me ssa ge
pointer(LOPT)
Me ssa ge bu ffer 5
Me ssa ge bu ffer 8
Me ssa ge bu ffer 4
Me ssa ge bu ffer 3
Me ssa ge bu ffer 7
Me ssa ge bu ffer 14
Me ssa ge bu ffer 5
Me ssa ge bu ffer 8
Me ssa ge bu ffer 4
Me ssa ge bu ffer 3
Me ssa ge bu ffer 7
Me ssa ge bu ffer 10
Me ssa ge bu ffer 6 Me ssa ge bu ffer 6
TOVF = 1
LOPT i
s b locked
Event:
- CPU confirm
s TX completion
of me ssa ge bu ffer 6, 9 a nd 2
- TX completion of me ssa ge
bu ffer 3 a nd 4
L as t o u t-
me ssa ge
pointer
(LOPT)
Event:
- me
ssa ge bu ffer 11, 1 3 a nd 14
complete s tr a n s mi ss ion.
- Overflow s it ua tion occ u r s .
TOVF = 1 define s th a t LOPT e qua l s TOPT - 1 while me ssa ge bu ffer n u m b er s tored to element indic a ted b y LOPT - 1.