UPD784938 Datasheet, PDF (505/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
20.6.3 Slave transmission
Start
<1>
Broad-
casting
M address P S address P
A
Approx. 624 µ s (mode 1)
Control
6
P
A
Telegraph
length
P
A
Data 1
Approx. 390 µ s
(mode 1)
6
Data 1 P A Data 2
6
PA
6
Data n–1
5
P A Data n
<2>
PA
n = Final number of data bytes
Caution indicates that an interrupt (INTIE1) does not occur.
Initial preparation processing
Sets a unit address, telegraph length, and the first byte of the transmit data.
Communication start processing
Sets the bus control register (enables communication, slave transmission, and slave reception).
<1> Interrupt (INTIE2) occurrence
Judgment of occurrence of error
↓
Judgment of slave request
→ Error processing
Interrupt (INTIE2) occurrence
An interrupt occurs only when 0H, 4H, 5H, or 6H is received in the control field in the slave status.
Interrupt (INTIE1) occurrence^{Note 1}
The transmit data of the second byte and those that follow are written to the data register (DR) by macro service.
At this time, the data transfer direction is RAM (memory) → SFR (peripheral).
<2> Interrupt (INTIE2) occurrence
Judgment of occurrence of error →
↓
Judgment of end of communication →
↓
Judgment of end of frame
→
Error processing
End of communication processing
Re-communication processing^{Note 2}
Notes 1. If NACK is received from the master in the data field, an interrupt (INTIE1) is not issued to the CPU,
but the same data is retransmitted by hardware.
If the transmit data is not written in time during the period of writing the next data, a communication
error interrupt occurs due to occurrence of underrun, and communication is abnormally ended.
2. The vector interrupt processing in <2> judges whether the data has been correctly transmitted within
one frame. If the data has not been correctly transmitted (if the number of data to be transmitted in
one frame could not be transmitted), the data must be retransmitted in the next frame, or the continuation
of the data must be transmitted.
Preliminary User’s Manual U13987EJ1V0UM00
505