LC709004A Datasheet, PDF (8/13 Pages) ON Semiconductor – I/O-Expander for Microcontroller

LC709004A
(1) Initial communication modes
• Mode 0
1) Setting the RES pin to the low level initializes the system, sets the DOUT pin to the high level, and sets the DDR
register of all ports to 0 and the DTR register to 1. The output type of the ports is set to Nch-open drain and their
I/O state (Nch-Tr=OFF) to the "Hi-Z" (input mode) state.
2) When the RES pin is set high (reset) and the CS pin is set and held low for a certain period (TwlCS), the DDR is
fixed at 0. Subsequently, the LC709004A is placed in the data communication mode.
RES
CS
CLK
DIN
DOUT
DDR
DTR
P00 to P17
Hi-Z
*DDR and DTR denote the state of the internal registers.
Fig. 1
• Mode 1
1) When the RES pin is set to the low level, the LC709004A initializes the system, sets the DOUT pin to the high
level, and sets the DDR register of all ports to 0 and the DTR register to 1. The output type of the ports is set to
Nch-open drain and their I/O state (Nch-Tr=OFF) to the "Hi-Z" (input mode) state.
2) When the RES pins is set high (reset) and the CS pin is set low, the LC709004A gets ready for serial
communication.
3) The input data at P00 is sent directly to the DOUT pin on the first falling edge of the transmission clock signal
CLK. The data at pins P01 to P17 is loaded into the shift register on the rising edge of the next clock.
4) Subsequently, the ports' input data, which is loaded into the shift register on the falling edge of CLK, is placed at
the DOUT pin sequentially (P00→P07, P10→P17) in synchronization with the falling edges of CLK, starting at
port pin P00. In parallel with this operation, when data to be placed at the ports is supplied to the DIN pin
sequentially starting at the port pin P00 (P00→P07, P10→P17), it is loaded into the internal shift register in
synchronization with the rising edges of CLK.
5) When the CS pin is set high after the rising edge of the 16th clock, the data loaded in the shift register is loaded
into the DDR register which determines the I/O mode and output type of the data (serial data is loaded into the
DDR register after a reset is effected). Subsequently, the LC709004A controls serial data transmission and
reception in the data communication mode.
RES
CS
CLK
0
1
2
3
4
5
6
7
8
9 14 15
DIN
P00_DR P01_DR P02_DR P03_DR P04_DR P05_DR P06_DR P07_DR P10_DR P11_DR P16_DR P17_DR
DOUT
P00_DI P01_DI P02_DI P03_DI P04_D P05_DI P06_D P07_DI P10_DI P11_DI P16_DI P17_DI
DDR
DTR
P00 to P17
Hi-Z
Hi-Z
* PXX_DR denotes the input data to the port DDR identified by PXX.
* PXX_DI denotes the input data from the port pin identified by PXX.
Fig. 2
No.A0165-8/13