ST7066U
!"Function Description
#" System Interface
This chip has all two kinds of interface type with MPU : 4-bit bus and 8-bit bus. 4-bit bus or 8-bit bus is selected
by DL bit in the instruction register.
During read or write operation, two 8-bit registers are used. One is data register (DR), the other is instruction
register(IR).
The data register(DR) is used as temporary data storage place for being written into or read from
DDRAM/CGRAM, target RAM is selected by RAM address setting instruction. Each internal operation, reading
from or writing into RAM, is done automatically. So to speak, after MPU reads DR data, the data in the next
DDRAM/CGRAM address is transferred into DR automatically. Also after MPU writes data to DR, the data in DR
is transferred into DDRAM/CGRAM automatically.
The Instruction register(IR) is used only to store instruction code transferred from MPU. MPU cannot use it to
read instruction data.
To select register, use RS input pin in 4-bit/8-bit bus mode.
RS R/W
Operation
InstructionWriteoperation(MPUwritesInstructioncode
L
L
into IR)
L
H
H
H
L
H
Read Busy Flag(DB7) and address counter (DB0 ~ DB6)
Data Write operation (MPU writes data into DR)
Data Read operation (MPU reads data from DR)
Table 1. Various kinds of operations according to RS and R/W bits.
#" Busy Flag (BF)
When BF = "High”, it indicates that the internal operation is being processed. So during this time the next
instruction cannot be accepted. BF can be read, when RS = Low and R/W = High (Read Instruction Operation),
through DB7 port. Before executing the next instruction, be sure that BF is not High.
#" Address Counter (AC)
Address Counter(AC) stores DDRAM/CGRAM address, transferred from IR.
After writing into (reading from) DDRAM/CGRAM, AC is automatically increased (decreased) by 1.
When RS = "Low" and R/W = "High", AC can be read through DB0 ~ DB6 ports.
V2.0
2001/03/01
9/42
POWERTIP [ POWERTIP TECHNOLOGY ]
