1998 May 11
14
Philips Semiconductors
Product specification
8-bit microcontroller with DTMF
generator and 128 bytes EEPROM
PCD3359A
7.1.2
EEPROM A
DDRESS
R
EGISTER
(ADDR)
The EEPROM Address Register determines the EEPROM location to which an EEPROM access is directed.
As a whole, ADDR auto-increments after read and write cycles to EEPROM, but remains fixed after erase cycles. This
behaviour generates the correct ADDR contents for sequential read accesses and for sequential write or erase/write
accesses with intermediate page setup. Overflow of the 8-bit counter wraps around to zero.
Table 14
EEPROM Address Register, ADDR (address 01H, access type R/W)
Table 15
Description of ADDR bits
7.1.3
EEPROM D
ATA
R
EGISTER
(DATR)
Table 16
EEPROM Data Register (address 03H; access type R/W)
Table 17
Description of DATR bits
7.1.4
EEPROM T
EST
R
EGISTER
(TST)
The EEPROM Test Register is used for testing purposes during device manufacture. It must not be accessed by the
device user.
7.2
EEPROM latches
The four EEPROM latches (EEPROM Latch 0 to 3; Fig.5) cannot be read by user software. Due to their construction, the
latches can only be preset, but not cleared. Successive write operations through DATR to the EEPROM latches actually
perform a logical OR with the previously stored data in EEPROM. The EEPROM latches are reset at the conclusion of
any EEPROM cycle.
7
6
5
4
3
2
1
0
0
AD6
AD5
AD4
AD3
AD2
AD1
AD0
BIT
SYMBOL
AD6 to AD2
AD1 to AD0
DESCRIPTION
7
This bit is set to a logic 0.
AD2 to AD6 select one of 32 pages.
AD1 and AD0 are irrelevant during erase and write cycles. For read accesses, AD0 and
AD1 indicate the byte location within an EEPROM page. During page setup, finally, AD0
and AD1 select EEPROM Latch 0 to 3 whereas AD2 to AD6 are irrelevant. If increment
mode (Table 13) is active during page setup, the subcounter consisting of AD0 and AD1
increments after every write to an EEPROM latch, thus enhancing access to sequential
EEPROM latches. Incrementing stops when EEPROM Latch 3 is reached, i.e. when
AD0 and AD1 are both a logic 1.
6 to 2
1 to 0
7
6
5
4
3
2
1
0
D7
D6
D5
D4
D3
D2
D1
D0
BIT
SYMBOL
DESCRIPTION
7 to 0
D7 to D0
The EEPROM Data Register (DATR) is only a conceptual entity. A read operation from
DATR, reads out the EEPROM byte addressed by ADDR. On the other hand, a write
operation to DATR, loads data into the EEPROM latch (see Fig.5) defined by bits AD0
and AD1 of ADDR.