GSM7980 Syntec Semiconductor, GSM7980 Datasheet - Page 6

• Manufacturer Part Number: GSM7980
• Description: Dot Matrix LCD Controller/Driver
• Manufacturer: Syntec Semiconductor

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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.
Table 1. Various kinds of operations according to RS and R/W bits.
RS
L
L
H
H
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.
LCD Controller / Driver
RW
L
H
L
H
Operation
Instruction Write operation (MPU writes Instruction code
into IR)
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)
Syntek Semiconductor Co., Ltd.
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ISSUE DATE :
GSM7980