CAT1024, CAT1025
Immediate/Current Address Read
Sequential Read
The CAT1024 and CAT1025 address counter contains
the address of the last byte accessed, incremented by
one. In other words, if the last READ or WRITE access
was to address N, the READ immediately following
wouldaccessdatafromaddressN+1.ForN=E=255,the
counter will wrap around to zero and continue to clock
outvaliddata. AftertheCAT1024andCAT1025receives
its slave address information (with the R/W bit set to
one), it issues an acknowledge, then transmits the 8-bit
byte requested. The master device does not send an
acknowledge, but will generate a STOP condition.
The Sequential READ operation can be initiated by
either the Immediate Address READ or Selective READ
operations. After the CAT1024 and CAT1025 sends the
inital 8-bit byte requested, the Master will responds with
an acknowledge which tells the device it requires more
data.TheCAT1024andCAT1025willcontinuetooutput
an 8-bit byte for each acknowledge, thus sending the
STOP condition.
The data being transmitted from the CAT1024 and
CAT1025issentsequentiallywiththedatafromaddress
N followed by data from address N+1. The READ
operationaddresscounterincrementsalloftheCAT1024
and CAT1025 address bits so that the entire memory
array can be read during one operation.
Selective/Random Read
Selective/Random READ operations allow the Master
device to select at random any memory location for a
READ operation. The Master device first performs a
‘dummy’writeoperationbysendingtheSTARTcondition,
slave address and byte addresses of the location it
wishes to read. After the CAT1024 and CAT1025
acknowledges, the Master device sends the START
condition and the slave address again, this time with the
R/W bit set to one. The CAT1024 and CAT1025 then
responds with its acknowledge and sends the 8-bit byte
requested. The master device does not send an
acknowledge but will generate a STOP condition.
Figure 11. Selective Read Timing
S
T
A
R
T
S
T
A
R
T
S
T
O
P
BUS ACTIVITY:
MASTER
SLAVE
ADDRESS
BYTE
ADDRESS (n)
SLAVE
ADDRESS
SDA LINE
S
S
P
A
C
K
A
C
K
A
C
K
N
O
DATA n
A
C
K
Figure 12. Sequential Read Timing
S
T
O
P
BUS ACTIVITY:
MASTER
SLAVE
ADDRESS
DATA n
DATA n+1
DATA n+2
DATA n+x
SDA LINE
P
A
C
K
A
C
K
A
C
K
A
C
K
N
O
A
C
K
Doc No. 3008, Rev. M
13
CATALYST [ CATALYST SEMICONDUCTOR ]
