UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 90

• Manufacturer Part Number: UPD75238GJ
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC [NEC]

90
(4) Signals
Table 4-6 lists signals. Fig. 4-43 to 4-48 show operations of signals and flags.
(d) Slave address register (SVA)
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 a RESET is entered, the value of SVA is undefined. However, the value of SVA is preserved
when the RESET is entered in the standby mode.
• Slave address detection
• Error detection
[In the SBI mode]
SVA is used when the PD75238 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.
Cautions 1. Slave selection or nonselection state is detected by detecting a match for a slave
[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 PD75238 operating as the master
• When data is transferred with the PD75238 operating as a slave
2. When detecting selection/nonselection state without using an interrupt when WUP
address 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.
is 0, do not use the address match detection method. Instead, use transfer of
commands set in advance in a program.
PD75238