UPD75518 NEC, UPD75518 Datasheet - Page 94

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

94
(4) Slave address register (SVA)
4.8.4 Signals
Table 4-10 lists signals. Fig. 4-38 to 4-43 show operations of signals and flags.
The slave address register (SVA) has the two functions described below.
SVA is manipulated using an 8-bit manipulation instruction. SVA allows only write operation.
When the RESET signal is entered, the value of SVA is undefined. However, the value of SVA is preserved
when the RESET signal is entered in the standby mode.
• Slave address detection
Cautions 1. Slave selection or nonselection state is detected by detecting a match for a slave address
• Error detection
[In the SBI mode]
SVA is used when the PD75518(A) is connected as a slave device to the serial bus. SVA is an 8-bit
register for a slave to set its slave address (number assigned to it). The master outputs a slave address
to the connected slaves to select a particular slave. Two data values (a slave address output from the
master and the value of SVA) are compared with each other by the address comparator. If a match
is found, the slave is selected.
At this time, bit 6 (COI) of serial operation mode register 0 (CSIM0) is set to 1.
[In the two-wire serial I/O mode or SBI mode]
SVA detects an error in either of the following cases:
• When addresses, commands, or data is transferred with the PD75518(A) operating as the master
• When data is transferred with the PD75518(A) operating as a slave
2. When detecting selection/nonselection state without using an interrupt when WUP is 0,
received after bus release (in the state of RELD = 1).
For this match detection, an address match interrupt (IRQCSI0) generated when WUP is set
to 1 is usually used. So detect selection/nonselection state by slave address when WUP
is set to 1.
do not use the address match detection method. Instead, use transfer of commands set
in advance in a program.
PD75518(A)