PCA8565BS NXP [NXP Semiconductors], PCA8565BS Datasheet - Page 24

• Manufacturer Part Number: PCA8565BS
• Description: Real time clock/calendar
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA8565_2
Product data sheet
Fig 19. Master reads after setting word address (write word address; read data)
S
SLAVE ADDRESS
10.5.3 Interface watchdog timer
During read/write operations, the time counting circuits are frozen. To prevent a situation
where the accessing device becomes locked and does not clear the interface, the
PCA8565 has a built in watchdog timer. Should the interface be active for more than 1 s
from the time a valid slave address is transmitted, then the PCA8565 will automatically
clear the interface and allow the time counting circuits to continue counting. Under a
correct data transfer, the watchdog timer is stopped on receipt of a START or STOP
condition.
The watchdog is implemented to prevent the excessive loss of time due to interface
access failure e.g. if main power is removed from a battery backed-up system during an
interface access.
Each time the watchdog period is exceeded, 1 s will be lost from the time counters. The
watchdog will trigger between 1 s and 2 s after receiving a valid slave address.
acknowledgement
Fig 20. Master reads slave immediately after first byte (read mode)
R/W
from slave
0 A
S
WORD ADDRESS
SLAVE ADDRESS
at this moment master transmitter
acknowledgement
Rev. 02 — 16 June 2009
becomes master receiver and
from slave
becomes slave transmitter
acknowledgement
A
PCA8565 slave receiver
R/W
from slave
1 A
S
SLAVE ADDRESS
n bytes
DATA
acknowledgement
acknowledgement
auto increment
word address
from master
R/W
from slave
1
A
A
last byte
n bytes
DATA
DATA
last byte
Real time clock/calendar
memory word address
DATA
no acknowledgement
auto increment
memory word address
acknowledgement
auto increment
word address
no acknowledgement
from master
auto increment
from master
PCA8565
© NXP B.V. 2009. All rights reserved.
from master
A
1
mgl665
1
001aaj743
P
P
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