CHAPTER 18 IEBus CONTROLLER (V850/SC2)
532
User’s Manual U15109EJ3V0UD
(6) IEBus telegraph length register (DLR)
(a) When transmission unit ... Master transmission, slave transmission
The data of this register is reflected in the data transmitted in the telegraph length field and indicates the
number of bytes of the transmit data.
This register must be set in advance before transmission.
(b) When reception unit ... Master reception, slave reception
The receive data in the telegraph length field transmitted from the transmission unit is written to this
register.
Remark
The IEBus telegraph length register is divided into a writing side and a reading side, making it
impossible for the written data to be readout as is. Only data received via IEBus
communication can be readout.
After reset: 01H
R/W
Address: FFFFF3EAH
7
6
5
4
3
2
1
0
DLR
Bit
7
6
5
4
3
2
1
0
Setting
value
Number of communication
data bytes
0
0
0
0
0
0
0
1
01H
1 byte
0
0
0
0
0
0
1
0
02H
2 bytes
:
:
:
:
:
:
:
:
:
:
0
0
1
0
0
0
0
0
20H
32 bytes
:
:
:
:
:
:
:
:
:
:
1
1
1
1
1
1
1
1
FFH
255 bytes
0
0
0
0
0
0
0
0
00H
256 bytes
Cautions 1. If the master issues a request “0H, 4H, 5H, or 6H” to transmit a slave status and lock
address (higher 4 bits, lower 8 bits), the contents of this register are set to “01H” by
hardware; therefore, the CPU does not have to set this register.
2. In the case of defeat in a bus conflict and a slave status request is received from the
unit that won, DLR is fixed to “01H”. Therefore, if a re-request of the master follows,
the appointed telegraph length must be set to DLR.