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CHAPTER 4 EEPROM
4.3 EEPROM Control Register
EEPROM is controlled with the EEPROM write control register (EEWC).
EEWC is set with either a 1-bit or 8-bit memory manipulation instruction.
RESET input sets EEWC to 00H.
Figure 4-2. EEPROM Write Control Register (EEWC) Format
Address: FF90H After Reset : 00H R/W
Symbol
7
6
5
4
3
2
1
0
EEWC
0
0
EWCS1
EWCS0
0
EWCC
EWST
EWE
EWCS1
EWCS0
EEPROM Write Time
0
0
(2
14
+ 2
10
)/f
X
Note 1
0
1
(2
15
+ 2
11
)/f
X
Note 2
Other than above
Setting prohibited
EWCC
EEPROM Operation Control
0
Operating mode
1
EEPROM stop
EWST
EEPROM Write Status
0
Not currently writing to EEPROM (EEPROM write/read is enabled. However, when
EWE = 0, write is disabled)
1
Currently writing to EEPROM (EEPROM write/read is disabled)
EWE
EEPROM Write Operation Control
0
EEPROM write disabled
1
EEPROM write enabled
Notes 1. Set the main system clock frequency (f
X
) in the range of 4 to 5.120 MHz.
2. Set the main system clock frequency (f
X
) in the range of 5.364 to 8.38 MHz.
Cautions 1. If the main system clock frequency is set in the range of 5.120 < f
X
< 5.364 MHz, the EEPROM
cannot be used.
2. When EWE is cleared (to 0) during EEPROM writing, writing is immediately interrupted.
Data that was being written becomes undefined. Be sure to clear EWE before stopping the
main system clock during the write period.
3. After EWCC is cleared (to 0), set a wait time of 20
µ
s or more by software to read EEPROM
contents.
4. Be sure to check that EWST is 0 before performing EEPROM access.
5. Bits 3, 6, and 7 must be set to 0.
Summary of Contents for mPD780973 Series
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