NEC PD754144 - Manual (Page 85)

CHAPTER 5 EEPROM
85 User’s Manual U10676EJ3V0UM
5.5.3 Write manipulation
Use the following procedure to write to EEPROM.
Any instruction other than one related to EEPROM writing can be executed even during an EEPROM write
operation.
EWST, EWTC and EWE can be set simultaneously by an 8-bit memory manipulation instruction to EWC.
<1> Check that the read status (EWST) is 0 (write enabled = currently not being written).
<2> Use EWTC4 to EWTC6 to set write time.
<3> Set the write enable/disable control bit (EWE) to 1 (write enabled).
<4> Execute the write instruction.
Figure 5-3. EEPROM Write Control Register in EEPROM Write Manipulation
ERE
7
EWTC6
6
EWTC5
5
EWTC4
4
EWE
3
EWST
2
–
1
–
0
FCEH
Address
EWC
Symbol
Operating mode selection bit
ERE EWE EWST Mode
0 1 0 EEPROM write enabled mode
Dedicated EEPROM write timer clock selection bit
EWTC6 EWTC5 EWTC4 Count clock selection
0 0 0 18 × 2 13 /f X
0 0 1 18 × 2 12 /f X
0 1 0 18 × 2 11 /f
X
0 1 1 18 × 2 10 /f X
1 0 0 18 × 2 9 /f
X
1 0 1 18 × 2 8 /f
X
Other than above Setting prohibited
f
X
= System clock oscillation frequency