UPD784938 Datasheet, PDF (493/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
• Slave request flag (SLVRQ) ... Bit 6
This flag indicates whether the master has issued a slave request.
• Contention flag (ARBIT) ... Bit 5
This flag indicates the result of contention.
[Set/reset condition]
Set: Set if the data output by a unit does not coincide with the data on the bus line during the arbitration period
after the master request has been made.
Reset: Cleared at start bit timing
• Broadcasting communication flag (ALLTRANS)... Bit 4
This flag indicates if the unit is performing broadcasting communication. The contents of the flag are initialized upon
detection of the start bit of each frame, and updated to the broadcasting field.
The set/bit conditions change depending on the broadcasting field bit reception data at all times except initialization
(reset) through system reset.
[Set/reset condition]
Set: Upon reception of “broadcasting” in broadcasting field
Reset: Upon reception of “individual” in broadcasting field, or upon input of system reset.
Caution Update of the broadcasting communication flag is performed regardless of whether or not the
communication target is the unit address.
Figure 20-23. Broadcasting Communication Flag Operation Example
IEBus
sequence
Start
Broad-
casting
M11
M10
Start
Broad-
casting
M11
M10
INTIE2
Set
No reset with start bit
Reset
• ACK transmission flag (ACK) ... Bit 3
This flag indicates whether ACK is transmitted during the ACK period of each field while the unit serves as a reception
unit. The content of the flag is updated during the ACK period of each frame.
If the internal circuit is initialized due to the occurrence of a parity error, the content of the flag cannot be updated
during the ACK period of the field.
• Lock status flag (LOCK) ... Bit 2
This flag indicates whether the unit is locked.
[Set/reset condition]
Set: Set if lock specifications “3H, 6H, AH, and BH” are received in the control field, and if the communication
end flag is “L” and frame end flag is “H”.
Reset: If the communication enable flag is cleared.
If unlocking commands “3H, 6H, AH, and BH” are received by the control field and the communication
end flag is set.
Caution Locking or unlocking is not performed during broadcasting communication.
Preliminary User’s Manual U13987EJ1V0UM00
493