5
LH155BA
1.3. System Bus Pins
SYMBOL
D
7
-D
0
I/O
I/O
DESCRIPTION
CSB
I
Chip selection input pin that decoded address bus signal is input.
Distinguishes display RAM data/commands of D
7
to D
0
data transferred from MPU.
0 : The data of D
7
to D
0
show the display RAM data.
1 : The data of D
7
to D
0
show the command data.
Initialized by setting to "L". The reset signals of the system are normally input. Reset
operation is performed in accordance with RESB signal level.
RS
I
RDB
(E)
I
In connecting to 80-family MPU :
This RDB is a pin for connecting the RDB signal of 80-family MPU. When the
signal enters in the "L" state, the data bus of this IC turns to the "output" state.
In connecting to 68-family MPU :
This RDB becomes a pin for connecting the enable clock signal of 68-family MPU.
When the signal enters in the "H" state, the data bus of this IC turns to the "active"
state.
In connecting to 80-family MPU :
This WRB is a pin for connecting the WRB signal of 80-family MPU, and when
WRB signal is "L", this pin is "active".
The data bus signal is input at the rising edge of WRB signal.
In connecting to 68-family MPU :
This WRB becomes a pin for connecting the R/W signal of controlling read/write of
68-family MPU.
R/W = "H" : Read
R/W = "L" : Write
MPU interface-type shift pin.
M86 = "H" : 68-family interface
M86 = "L" : 80-family interface
Fixed to either "H" or "L".
Serial-data input pin at time of serial interface selection.
Serial clock pin at time of serial interface selection.
Used to shift the SDA data by using the rising edge of SCL.
Used to convert into 8-bit data by using the 8th clock at the rising edge of SCL in
serial-to-parallel data processing.
After data-transferring, or when making no access, be sure to set to "L".
Used to shift between parallel interface and serial interface.
P/S
Chip selection Data identification
Data
H
CSB
RS
D
7
-D
0
L
CSB
RS
SDA
WRB
(R/W)
I
I
M86
SDA
I
SCL
I
8-bit bi-directional data bus, connected to 8-bit MPU data bus.
I
RESB
P/S = "H" for parallel input. Fix SDA and SCL pins to either "H" or "L".
P/S = "L" for serial input. Fix D
7
to D
0
pins to High-Z, RDB and WRB pins to either
"H" or "L".
For testing. Fix to "L".
I
P/S
TEST
I
Read/Write
Serial clock
RDB, WRB
Write only
–
SCL