NEC PD754244 Manuel D’Utilisation

CHAPTER 5 EEPROM

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

µPD754144 ··· 18 × 2

(4.6 ms: f

= 1.0 MHz)

With

µPD754244 ··· 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

µA 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

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

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

µPD75048 is not provided.