UPD784938 Datasheet, PDF (474/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
The operation of the telegraph length field differs depending on whether the master transmits (when control bit 3 is
1) or receives (when control bit 3 is 0) data.
<1> When master transmits data
The telegraph length bit and parity bit are output by the master unit. When the slave unit detects that the parity
is even, it outputs the acknowledge signal, and starts outputting the data field. During broadcasting
communication, however, the slave unit does not output the acknowledge signal.
If the parity is odd, the slave unit judges that the telegraph length bit has not been correctly received, does not
output the acknowledge signal, and returns to the standby (monitor) status. At this time, the master unit also
returns to the standby status, and communication ends.
<2> When master receives data
The telegraph length bit and parity bit are output by the slave unit. If the master unit detects that the parity bit
is even, it outputs the acknowledge signal.
If the parity bit is odd, the master unit judges that the telegraph length bit has not been correctly received, does
not output the acknowledge signal, and returns to the standby status. At this time, the slave unit also returns
to the standby status, and communication ends.
(7) Data field
This is data output by the transmission side.
The master unit transmits or receives data to or from a slave unit by using the data field.
The configuration of the data field is as shown in Figure 20-6.
Figure 20-6. Data Field
MSB
Data field (number specified by telegraph length field)
One data
Control bit (8 bits)
Parity ACK
Parity ACK
LSB
Following the data bit, the parity bit and acknowledge bit are respectively output by the master unit and slave unit.
Broadcasting communication is used only when the master unit transmits data. At this time, the acknowledge bit is
ignored.
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Preliminary User’s Manual U13987EJ1V0UM00