72720YV Datasheet, PDF (13/14 Pages) Sanyo Semicon Device – Single-Chip RDS Signal-Processing System IC

LC72720Y, 72720YV
Parameter
Data setup time
Data hold time
Clock low-level time
Clock high-level time
CE wait time
CE setup time
CE hold time
CE high-level time
Data latch transition time
Data output time
Symbol
Conditions
t_SU DI, CL
t_HD DI, CL
t_CL
CL
t_CH CL
t_EL
CE, CL
t_ES CE, CL
t_EH CE, CL
t_CE
CE
t_LC
t_DC DO, CL _{Differs with the value of}
t_DH
DO, CE ^{the pull-up resistor used.}
min
0.75
0.75
0.75
0.75
0.75
0.75
0.75
Ratings
typ
Unit
max
μs
μs
μs
μs
μs
μs
μs
20 ms
1.15
μs
0.46
μs
0.46
μs
DO pin operation
This IC incorporates a RAM data buffer that can hold up to 24 blocks of data. At the point where one block of data is
written to this RAM, the IC issues a read request by switching the DO pin from high to low.
The DO pin always goes high for a fixed period (Tdo = 265 μs) after a readout and CE goes low. When all the data in the
data buffer has been read out, the DO pin is held in the high state until a new block of data has been written to the RAM. If
there is data that has not yet been read remaining in the data buffer, the DO pin goes low after the Tdo time has elapsed.
After a synchronization reset, the DO pin is held high until synchronization is established. It goes low at the point where
the IC synchronizes.
1. When the DO pin is high following the 265 μs period (Tdo) after data is read out
Here, the buffer is in the empty state, i.e. the state where new data has not been written. After this, when the DO pin
goes low, applications are guaranteed to be able to read out that data without it being overwritten by new data if they
start a readout operation within 480 ms of DO going low.
Tdo
CE pin
DO pin
T
(Last data) - 1
Last data
New data
DO check (Tdo < T)
A13219
2. When DO goes low 265 μs after data is read out
Here, there is data that has not been read out remaining in the data buffer. In this case, applications are guaranteed to
be able to read out that data without it being overwritten by new data if they start a readout operation within 20 ms of
DO going low. (Note that this is the worst case condition.)
Tdo
CE pin
T
DO pin
(Last data) - 2 (Last data) - 1
Last data
A13220
DO check (Tdo < T)
Notes: 1. Although an application can determine whether or not there is data remaining in the buffer by checking the DO
level with the above timing, checking the RE and RF flags in the serial data is a preferable method.
2. Applications are not limited to reading out one block of data at a time, but rather can read out multiple blocks
of data continuously as described above. When using this method, if an application references the RE and RF
flags in the data while reading out data, it can determine the amount of data remaining. However, the length of
the period for data readout (the period the CE pin remains high) must be kept under 20 ms.
3. If the DO pin is shared with other ICs that use the CCB interface, the application must identify which IC
issued the readout request. One method is to read out data from the LC72720Y and either check whether
meaningful data has been read (if the LC72720Y is not requesting a read, data consisting of all zeros will be
read out) or check whether the DO level goes low within the 265 μs following the completion of the read (if the
DO pin goes low, then the request was from another IC).
No. 6488-13/14