CAT9554 Datasheet, PDF (10/16 Pages) Catalyst Semiconductor – Catalyst Semiconductor

CAT9554, CAT9554A
The output port register sets the outgoing logic levels
of the I/O ports, defined as outputs by the
configuration register. Bit values in this register have
no effect on I/O pins defined as inputs. Reads from
the output port register reflect the value that is in the
flip-flop controlling the output, not the actual I/O
pin value.
The polarity inversion register allows the user to invert
the polarity of the input port register data. If a bit in
this register is set (“1”) the corresponding input port
data is inverted. If a bit in the polarity inversion
register is cleared (“0”), the original input port polarity
is retained.
The configuration register sets the directions of the
ports. Set the bit in the configuration register to enable
the corresponding port pin as an input with a high
impedance output driver. If a bit in this register is
cleared, the corresponding port pin is enabled as an
output. At power-up, the I/Os are configured as inputs
with a weak pull-up resistor to V_CC.
Data is transmitted to the CAT9554/9554A registers
using the write mode shown in Figure 9 and Figure 10.
The CAT9554/9554A registers are read according to
the timing diagrams shown in Figure 11 and Figure
12. Once a command byte has been sent, the register
which was addressed will continue to be accessed by
reads until a new command byte will be sent.
SCL
123456 789
slave address
R/W
command byte
SDA S 0 1 0 0 A2 A1 A0 0 _{A 0 0 0 0 0 0 0 1} A
start condition
WRITE TO
PORT
acknowledge
from slave
acknowledge from slave
DATA OUT
FROM PO RT
data to port
DATA 1
acknowledge from slave
AP
stop
condition
DATA 1 VALID
tpv
Figure 9. Write to Output Port Register
SCL
12 34 56 78 9
slave address
R/W
command byte
SDA _{S 0 1 0 0 A2 A1 A0 0 A 0 0 0 0 0 0 1 1/0} A
start condition
WRITE TO
REGISTER
acknowledge
from slave
acknowledge from slave
data to register
DATA 1
acknowledge from slave
AP
stop
condition
Figure 10. Write to Configuration or Polarity Inversion Register
Doc. No. MD-9002 Rev. F
10
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Characteristics subject to change without notice