UPD784938 Datasheet, PDF (476/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
During broadcast communication, however, the content of the acknowledge bit is ignored.
<1> Last acknowledge bit of slave address field
The last acknowledge bit of the slave address field serves as NACK in any of the following cases, and transmission
is stopped.
• If the parity of the master address bit or slave address bit is incorrect
• If a timing error (error in bit format) occurs
• If a slave unit does not exist
<2> Last acknowledge bit of control field
The last acknowledge bit of the control field serves as NACK in any of the following cases, and transmission is
stopped.
• If the parity of the control bit is incorrect
• When control bit 3 is “1” (write operation) when the slave receive enable flag (ENSLVRX)^Note is not set
• When control bits for which ENSLVRX^Note is not set are data read (3H, 7H)
• If control bits 3H, 6H, 7H, AH, BH, EH, or FH are requested from a unit other than one for which lock has been
set
• If the control bit indicates reading of a lock address (4H or 5H) even when locking is not set
• If a timing error occurs
• If the control bit is undefined
Note Bit 3 of the bus control register (BCR)
Cautions 1. When the slave status request control data is received even if the slave transmit enable
flag (ENSLVTX) is not set, ACK is always returned.
2. When data/command write control data is received even when the slave receive enable
flag (ENSLVRX) is not set, the control field acknowledge bit returns NACK.
Prohibiting receive operations (stopping communication) using ENSLVRX is limited to
individual sommunication. In the case of broadcast communication, communication
continues until a data request interrupt (INTIE1) or end interrupt (INTIE2) is generated.
<3> Last acknowledge bit of telegraph length field
The last acknowledge bit of the telegraph length field serves as NACK in any of the following cases, and
transmission is stopped.
• If the parity of the telegraph length bit is incorrect
• If a timing error occurs
<4> Last acknowledge bit of data field
The last acknowledge bit of the data field serves as NACK in any of the following cases, and transmission is
stopped.
• If the parity of the data bit is incorrect^Note
• If a timing error occurs after the preceding acknowledge bit has been transmitted
• When receive data is stored in the data register (DR), and no more data can be accepted^Note.
Note In this case, for the individual communication, if the maximum number of transmission bytes is a value
within the range that can be transmitted in one frame, the transmission side performs transmission of
that data field again. In the case of broadcast communication, the transmission side does not perform
transmission of that data field again, and a transmission error occurs on the receiving side and reception
is stopped.
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Preliminary User’s Manual U13987EJ1V0UM00