UPD72042BGT NEC [NEC], UPD72042BGT Datasheet - Page 18

• Manufacturer Part Number: UPD72042BGT
• Description: LSI DEVICE FOR Inter Equipment Bus (IEBus) PROTOCOL CONTROL
• Manufacturer: NEC [NEC]

master unit that requested the lock, unless the value of the control bits is one of the values listed in Table 2-4. Then,
the unit does not output the acknowledge bit.
18
(1) Reading the slave status (SSR) (control bits: 0H, 6H)
Notes 1. The transfer direction of the data-length bits of the subsequent data-length field and data in the data
Once a unit has been locked by a master unit, the locked unit rejects the control bits received from other than the
AH
BH
CH
DH
EH
0H
1H
2H
3H
4H
5H
6H
7H
8H
9H
FH
0H
4H
5H
A master unit can read the slave status (0H, 6H) to determine why the slave unit did not return the acknowledge
bit (ACK).
The slave status is determined from the result of the communication last performed by the slave unit.
All slave units can provide slave status information.
Table 2-5 lists the slave status meanings.
2. The values of control bits 3H, 6H, AH, and BH specify locking and unlocking. When an undefined value,
Bit 3
field changes according to the value of bit 3 (MSB).
When bit 3 is 1: Transfer from the master unit to the slave unit
When bit 3 is 0: Transfer from the slave unit to the master unit
1H, 2H, 8H, 9H, CH, or DH, is transmitted, no acknowledge signal is returned.
Bit 3
Note 1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
Bit 2
Bit 2
Table 2-4 Control Field Acceptable to a Locked Slave Unit
0
0
0
0
1
1
1
1
0
0
1
1
1
0
0
1
0
1
1
Bit 1
Bit 1
Table 2-3 Meanings of the Control Bits
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
0
Bit 0
Bit 0
Data Sheet S13990EJ3V0DS
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
1
Read slave status (SSR)
Undefined
Undefined
Read data and locking
Read lock address (low-order 8 bits)
Read lock address (high-order 4 bits)
Read slave status (SSR) and unlocking
Read data
Undefined
Undefined
Write command and locking
Write data and locking
Undefined
Undefined
Write command
Write data
Read slave status
Read lock address (low-order 8 bits)
Read lock address (high-order 4 bits)
Function
Function
Note 2
PD72042B