Rainbow Electronics HD44780 - Manual (Page 3)

HD44780U
3
HD44780U Block Diagram
Display
data RAM
(DDRAM)
80
×
8 bits
Character
generator
ROM
(CGROM)
9,920 bits
Character
generator
RAM
(CGRAM)
64 bytes
Instruction
register (IR)
Timing
generator
Common
signal
driver
16-bit
shift
register
Segment
signal
driver
40-bit
latch
circuit
40-bit
shift
register
Parallel/serial converter
and
attribute circuit
LCD drive
voltage
selector
Address
counter
MPU
inter-
face
Input/
output
buffer
Data
register
(DR)
Cursor
and
blink
controller
CPG
CL1
CL2
M
D
RS
R/W
DB4 to
DB7
E
Instruction
decoder
OSC1 OSC2
COM1 to
COM16
SEG1 to
SEG40
8
8 8
7
40
5 5
7
8
7
8
7
V
CC
GND
V1 V2 V3 V4 V5
DB0 to
DB3
Reset
circuit
ACL
8
Busy
flag