CHAPTER 5 EEPROM
82
User’s Manual U10676EJ3V0UM
Cautions
1. The write time depends on the system clock oscillation frequency.
2. Set EWTC4-EWTC6 so that the write time is as follows.
With
µ
PD754144 ··· 18
×
2
8
/f
CC
(4.6 ms: f
CC
= 1.0 MHz)
With
µ
PD754244 ··· 4.0 ms MIN., 10.0 ms MAX.
Clear EWE to 0 after writing.
3. Be sure to clear (0) the ERE flag before executing a STOP instruction to disable reading. If
the ERE flag is set (1), a current of approximately 10
µ
A always flows in the read circuit.
Therefore, be sure to clear (0) the ERE flag before executing a STOP instruction to stop the
current supply to the read circuit.
4. Be sure to clear (0) the EWE flag before executing a STOP instruction to disable writing.
EWC is set by an 8-bit memory manipulation instruction.
Bits 4 to 6 of EWC are the dedicated EEPROM write timer clock selection bits (EWTC).
EWTC sets the count clock when EEPROM automatic erasure/automatic writing is performed. EEPROM performs
automatic erasure/automatic writing for each time set by EWTC.
Bit 2 of EWC is a write status flag (EWST). This flag can be used to check in 1-bit units whether writing is currently
performed or writing is possible. When writing is started, EWST is automatically write disabled (1). A bit memory
manipulation instruction is used to check this.
RESET input clears all EWC bits to 0.
Example
EEPROM is write enabled and the write time is set to 18
×
2
8
/f
X
.
SEL
MB15
MOV
XA, #01011000B
MOV
EWC, XA
5.4 Interrupt Related to EEPROM Control
Table 5-5 shows the interrupt related to EEPROM control.
For the details of the interrupt function, refer to
CHAPTER 7 INTERRUPT AND TEST FUNCTIONS.
Table 5-1. Interrupt Related to EEPROM Control
Interrupt Source
EEPROM Interrupt EEPROM Interrupt
Vector Table
Interrupt Request Flag
Request Flag
Request Flag
Address
Setting Source
INTEE
IRQEE
IEEE
VRQ7
When the write time set by
EEPROM write
(000EH)
EWC has elapsed.
end interrupt
Caution The INTOW interrupt (EEPROM overwrite interrupt) used in the
µ
PD75048 is not provided.