UPD784938 Datasheet, PDF (487/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
(5) Control data register (CDR)
[During master unit]
The data of the low-order 4 bits is reflected on the data transmitted in the control field. During master request, this
register must be set in advance before starting communication.
[During slave unit]
The data received in the control field is written to the low-order 4 bits.
When the status transmission flag (STATUS) is set, an interrupt (INTIE2) is issued, and each processing should
be performed by software, according to the value of the low-order 4 bits of this register.
Figure 20-15. Control Data Register (CDR) Format
7
6
5
4
3
2
1
0 Address After reset R/W
CDR 0
0
0
0 MOD SELCL2 SELCL1 SELCL0 0FFB8H 01H R/W
MOD SELCL2 SELCL1 SELCL0
Function
0
0
0
0 Reads slave status
0
0
0
1 Undefined
0
0
1
0 Undefined
0
0
1
1 Reads data and locks
0
1
0
0 Reads lock address (low-order 8 bits)
0
1
0
1 Reads lock address (low-order 4 bits)
0
1
1
0 Reads slave status and unlocks
0
1
1
1 Reads data
1
0
0
0 Undefined
1
0
0
1 Undefined
1
0
1
0 Writes command and locks
1
0
1
1 Writes data and locks
1
1
0
0 Undefined
1
1
0
1 Undefined
1
1
1
0 Writes command
1
1
1
1 Writes data
Cautions 1. Because the slave unit must judge whether the received data is a “command” or “data”, it must
read the value of this register after completing communication.
2. The Read Modify Write instruction (such as XCH and ROL4) cannot be used for CDR.
3. If the master unit sets an undefined value, NACK is returned from the slave unit, and
communication is aborted. During broadcasting communication, however, the master unit
continues communication without recognizing ACK/NACK; therefore, make sure not to set an
undefined value to this register during broadcasting communication.
4. In the case of defeat in a bus conflict and a slave status request is received from the unit that
won, telegraph length register (DLR) is fixed to “01H”. Therefore, in a re-request of the master
follows, the appointed telegraph length must be set to DLR.
Preliminary User’s Manual U13987EJ1V0UM00
487