Automatic Block Transmission (Abt) - NEC V850E/RS1 User Manual

Last out-
message
pointer
(LOPT)
Last out-
message
pointer
(LOPT)

16.10.3 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 OPMODE[2:0] of the CnCTRL register to 010B, "normal operation mode with automatic 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 MT[2:0] bits to 000B. Be sure to set the same ID for the message buffers for ATB 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,
TRQ of the next message buffer, message buffer 1, is set automatically. In this way, transmission is exe-
cuted 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.
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Chapter 16 FCAN Controller
Figure 16-53: Transmit History List
Transmit history list (THL)
7
6
Event:
5
- CPU confirms Tx completion
4
of message buffer 6, 9, and 2.
Message buffer 7
3 - Tx completion of message
buffer 3, and 4.
Message buffer 2
2
Message buffer 9
1
Message buffer 6
0
Transmit
history list
get pointer
(TGPT)
Transmit history list (THL)
Message buffer 5
7
Message buffer 8
6
Message buffer 4
5
Message buffer 3
4
Message buffer 7
3
Transmit
2
history list
Message buffer 10
1
get pointer
Message buffer 6
0
(TGPT)
TOVF bit = 1
LOPT is blocked
TOVF bit = 1 denotes that LOPT equals TGPT - 1 while message buffer number stored to element indicated by LOPT - 1.
User's Manual U16702EE3V2UD00
Last out-
message
pointer
(LOPT)
Event:
- Message buffer 8, 5, 6, and 10 completes transmission.
- THL is full.
- TOVF bit is set to 1.
Event:
- Message buffer11, 13, and 14
completes transmission.
- Overflow situation occurs.
Last out-
message
pointer
(LOPT)
Transmit history list (THL)
7
6
Message buffer 4
5
Message buffer 3
4
Message buffer 7
3
Transmit
2
history list
1
get pointer
0
(TGPT)
Transmit history list (THL)
Message buffer 5
7
Message buffer 8
6
Message buffer 4
5
Message buffer 3
4
Message buffer 7
3
Transmit
2
history list
Message buffer 14
1
get pointer
Message buffer 6
0
(TGPT)
TOVF bit = 1
LOPT is blocked
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