LC7982A Datasheet, PDF (11/18 Pages) Sanyo Semicon Device – LCD Dot Matrix Graphics Display Controller

LC7982A
• Cursor address (high order) setting (RAM read/write high-order address)
Register
R/W RS DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Instruction register
01 00001011
Cursor address counter
(High-order byte)
00
(Cursor address high-order byte) binary
These instructions together write the cursor address value into the cursor address register. The cursor address indicates
the address used for refering to RAM for the display data or character code. That is, the data at the address specified by
the cursor address will be read or written. In character display mode, the cursor is displayed at the position specified by
the cursor address.
While the cursor address is a 16-bit value formed from high-order and low-order bytes, applications must only use
cursor addresses that obey the following restrictions.
When the application rewrites (sets)
1 _{both the low-order and high-order bytes.}
The application must first set the low-order
byte and then set the high-order byte.
When the application only needs to rewrite After writing the low-order byte, the appli-
2 _{the low-order byte}
cation must also write the high-order byte.
The application should simply write the
When the application only needs to rewrite high-order byte.
3 _{the high-order byte}
There is no need for it to write the
low-order byte.
The cursor address counter is a 16-bit increment-only counter with set and reset functions. When the nth bit changes
from 1 to 0, bit n+1 is incremented. When the low-order byte is set, if the set caused the MSB in the low-order byte to
change from 1 to 0, the LSB in the high-order byte will be incremented. Therefore, applications must set both the low-
order and the high-order bytes in that order when setting the cursor address.
• Display data write
Register
Instruction register
RAM
R/W RS
01
00
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
00001100
MSB (Pattern data or character code) LSB
When 8 bits of data are written by writing the instruction code 0CH to the instruction register when RS is 0, that data
will be written as either display data or a character code to the RAM address specified by the cursor address counter.
The value of the cursor address counter is incremented by 1 after the write.
• Display data read
Register
R/W RS DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
Instruction register
01 00001101
RAM
10
MSB (Pattern data or character code) LSB
Applications can read out data in RAM after the LC7982A has been set to the readout state by writing the instruction
code 0DH to the instruction register when RS is 0. The data readout procedure is described below.
When this instruction is executed, the contents of the data output register will be output from the pins DB0 to DB7.
After that, the RAM data specified by the cursor address will be transferred to the data output register. Additionally,
the cursor address will be incremented by 1. As a result, the correct data will not be read out on the first readout after
the cursor address is set, but the specified data will be read out on the second read. Accordingly, applications that read
data out after setting the cursor address must perform a single dummy read operation.
• Bit clear
Register
Instruction register
Bit clear
• Bit set
R/W RS
01
00
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
00001110
0 0 0 0 0 (N_B – 1) binary
Register
Instruction register
Bit set
R/W RS
01
00
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
00001111
0 0 0 0 0 (N_B – 1) binary
The bit clear and bit set instructions set a specified bit in a byte in display data RAM to 0 or 1, respectively. The bit
clear instruction clears the bit specified by N_B to 0, and the bit set instruction sets the bit to 1. The RAM address is
determined by the cursor address, and the cursor address is automatically incremented by 1 after the instruction is
executed. N_B must be a value in the range 1 to 8. A value of 1 specifies the LSB and a value of 8 specifies the MSB.
No. 5946-11/18