ptn3500dh NXP Semiconductors, ptn3500dh Datasheet - Page 8

• Manufacturer Part Number: ptn3500dh
• Description: Maintenance And Control Device
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Read operations
PTN3500 read operations are initiated in an identical manner to
write operations with the exception that the memory slave address’
R/W bit is set to a one. There are three types of read operations;
current address, random and sequential.
Current Address Read (see Figure 14)
The PTN3500 contains an internal address counter that increments
after each read or write access, as a result if the last word accessed
was at address n then the address counter contains the address
n+1.
When the PTN3500 receives its memory slave address with the
R/W bit set to one it issues an acknowledge and uses the next eight
clocks to transmit the data contained at the address stored in the
address counter. The master ceases the transmission by issuing the
stop condition after the eighth bit. There is no ninth clock cycle for
the acknowledge.
Random Read (see Figure 15)
The PTN3500’s random read mode allows the address to be read
from to be specified by the master. This is done by performing a
dummy write to set the address counter to the location to be read.
2001 Jan 17
Maintenance and control device
SDA
SDA
START
CONDITION
START
CONDITION
S
S
1 0 1 0 A2 A1 A0
1 0 1 0 A2 A1 A0
(MEMORY)
(MEMORY)
ADDRESS
ADDRESS
SLAVE
SLAVE
R/W
R/W
0
1
A
A
ACKNOWLEDGE
FROM SLAVE
ACKNOWLEDGE
FROM SLAVE
SDA
FROM MEMORY
ADDRESS
START
CONDITION
S
Figure 14. Current Address Read
WORD
ACKNOWLEDGE
DATA n
DATA
1 0 1 0 A2A1A0 1 A
FROM SLAVE
Figure 16. Sequential Read
Figure 15. Random Read
(MEMORY)
ADDRESS
SLAVE
ACKNOWLEDGE
FROM MASTER
A
A
START
CONDITION
S
R/W
FROM MEMORY
8
1 0 1 0 A2 A1 A0 1
DATA n+1
ACKNOWLEDGE
FROM SLAVE
(MEMORY)
ADDRESS
DATA
The master must perform a byte write to the address location to be
read, but instead of transmitting the data after receiving the
acknowledge from the PTN3500 the master reissues the start
condition and memory slave address with the R/W bit set to one.
The PTN3500 will then transmit an acknowledge and use the next
eight clock cycles to transmit the data contained in the addressed
location. The master ceases the transmission by issuing the stop
condition after the eighth bit, omitting the ninth clock cycle
acknowledge.
Sequential Read (see Figure 16)
The PTN3500 sequential read is an extension of either the current
address read or random read. If the master doesn’t issue a stop
condition after it has received the eighth data bit, but instead issues
an acknowledge, the PTN3500 will increment the address counter
and use the next eight cycles to transmit the data from that location.
The master can continue this process to read the contents of the
entire memory. Upon reaching address 255 the counter will return to
address 0 and continue transmitting data until a stop condition is
received. The master ceases the transmission by issuing the stop
condition after the eighth bit, omitting the ninth clock cycle
acknowledge.
SLAVE
DATA FROM MEMORY
R/W
A
ACKNOWLEDGE
FROM MASTER
ACKNOWLEDGE
FROM SLAVE
A
DATA FROM MEMORY
FROM MEMORY
P
STOP
CONDITION
DATA N+X
DATA
STOP
CONDITION
P
P
STOP
CONDITION
SW00558
SW00557
Product specification
PTN3500
SW00556