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Serial Interface

Serial interfaces are typically used to connect the host-controllers to peripherals such as terminals and printers. The data (information) transfers in or out sequentially, one bit at a time using a single conductor, making it is a cost-effective interface.

GT-CP Serial Interface

One of three serial interfacing modes (UART, I2C, and SPI) can be selected via jumpers J5 and J6. For all modes, the SBUSY/ DTR signal reflects the receive buffer state, and the TRDY signal indicates if there is data currently held in the transmit buffer, so these signals can be used for flow control. All the data received is stored in the internal receive buffer and processed in the order it is recieved.

Jumper Selections and interface modes
J5 J6 Function
OPEN OPEN SPI mode
OPEN SHORT Factory Reserved
SHORT OPEN I2C mode
SHORT SHORT UART mode

•Please refer to the respective hardware specification to confirm the jumper location

Buffer Capacity
Receive Buffer 2,047 bytes
Transmit Buffer 127 bytes
SBUSY / DTR Signal Change Timing
SBUSY Change Interface ‘L’(READY)→‘H’(BUSY) ‘H’(BUSY) →‘L’(READY)
Receive buffer space UART / I2C 62 bytes or less 128 bytes or more
SPI 54 bytes or less
TRDY Signal Change Timing
TRDY READY(‘H’) EMPTY(‘L’)
Condition Data in transmit buffer No data in transmit buffer

UART

Jumper selection

J5 J6 Function
SHORT SHORT UART mode
J3 J4 Function
OPEN OPEN Set baud rate to 38,400 bps
OPEN SHORT Set baud rate to 19,200 bps
SHORT OPEN Set baud rate by memory switch setting
SHORT SHORT Set baud rate to 115,200 bps

Refer to the software spec to see the memory switch setting details

Interface Pin Assignments

Pin Number Signal name Function Direction
1 /RESET Hardware reset Input
2 (Do not connect) N/A Input
3 RxD Data receive Input
4 DTR Display busy Output *1
5 DSR Host busy Input
6 TxD Data send Output *1
7 TRDY Transmit ready Output *1
8 VCC Power Supply (5V) Input
9 GND Ground N/A

Note *1: Output is high-impedance (Hi-Z) + pull-up resistor (53kΩ typ.) during power-on, reset input, and display internal initialization.

Note: Except for the Power supply, all the signals are 3.3V

Protocol

Interface Conditions
Baud rate 4,800 to 115,200bps (set by jumper and/or memory switch function)
Default setting: 38,400bps Parity
None, even, odd (set by memory switch function) Default setting: None
Format Start (1 bit) + data (8 bit) + parity (0 or 1 bit) + stop (1 bit)
Communication Control Signal DSR, DTR, TRDY

•Data transmitted from the display is placed in the internal transmit buffer and sent, in order, when DSR = READY.

•TRDY signal does not need to be used.

Data Frame (With parity bit)

Data Frame (No parity bit)

SPI

Jumper selection

J5 J6 Function
OPEN OPEN SPI mode

Interface Pin Assignments

Pin Number Signal name Function Direction
1 /RESET Hardware reset Input
2 SCK Serial clock Input
3 MOSI Data receive Input
4 SBUSY Display busy Output *1
5 SSEL Host busy Input
6 MISO Data send Output *1
7 TRDY Transmit ready Output *1
8 VCC Power Supply (5V) Input
9 GND Ground N/A

Note *1: Output is high-impedance (Hi-Z) + pull-up resistor (53kΩ typ.) during power-on, reset input, and display internal initialization.

Note: Except for the Power supply, all the signals are 3.3V

Protocol

The display module operates as an SPI slave; data is sent and received in response to host (master) operations.

SSEL= 1 → 0 → 1 is one command sequence.
1st Byte Operation Mode
0x44 Data write (Host → Module)
0x54 Data read (Host ← Module)
0x58 Status read (Host ← Module)
Communication Parameters
Baud Rate Max. 8.3Mbps
Format SPI
Communication Control Signals SBUSY, TRDY

•The TRDY signal may be monitored, but the host (master) must still use the Status Read sequence before the Data Read sequence.p>

•The SBUSY signal can be monitored directly or via the Status Read sequence.

Data Write

When 0x44 is input as the first byte, the module receives the 2nd and subsequent bytes as data.

1st byte 2nd byte 3rd byte — n+1 byte
MOSI 0x44 Data(1) Data(2) — Data(n)
MISO – – – — –

Data Write Timing

Data Write Timing Details

Data Read

When 0x54 is input as the first byte, the module outputs valid data on the 3rd and subsequent bytes. The host must read the number of bytes reported by the immediately preceding Status Read command. The number of bytes reported by the Status Read command will be transmitted, with any unread bytes discarded.

1st byte 2nd byte 3rd byte — m+2 byte
MOSI 0x54 – – — –
MISO – 0x00 Data(1) — Data(m)

m: The number of data bytes reported by the Status Read command(TL of status byte).

Status Read

When 0x58 is input as the first byte, the module outputs status data. For the 3rd and any subsequent bytes, the most recent status data is provided.

1st byte 2nd byte — n byte
MOSI 0x58 – — –
MISO – Status Status Status

SBUSY: SBUSY signal

TL: Number of transmit data bytes available (maximum 63 bytes)

*: If b6 is 1, the status byte is invalid.

DaStatus and Data Read Timing

I2C

Jumper selection

J5 J6 Function
SHORT OPEN I2C mode
J0 J1 Function
OPEN OPEN I2C slave address = 50h
OPEN SHORT I2C slave address = 51h
SHORT OPEN I2C slave address = 52h
SHORT SHORT I2C slave address = 53h

Note: Module does not respond to the general call address (0x00).

Interface Pin Assignments

Pin Number Signal name Function Direction
1 /RESET Hardware reset Input
2 SCL Serial clock Input
3 SDA Data receive Input / Output
4 SBUSY Display busy Output *1
5 (Do not connect) N/A Input
6 (Do not connect) N/A Output *1
7 TRDY Transmit ready Output *1
8 VCC Power Supply (5V) Input
9 GND Ground N/A

Note *1: Output is high-impedance (Hi-Z) + pull-up resistor (53kΩ typ.) during power-on, reset input, and display internal initialization.

Note: Except for the Power supply, all the signals are 3.3V

Protocol

The display module operates as an SPI slave; data is sent and received in response to host (master) operations.

Communication Parameters
Baud Rate Max. 400kbps
Format I2C
Slave Address Set by jumper J0 and J1 (Default setting: 50h)
Supported Functions ACK response, clock stretch
Communication Control Signals SBUSY, TRDY, clock stretch

Note: If clock stretch is applied during processing of a command, the host (master) will not be able to send or receive any more data until command processing has finished.

If TRDY = EMPTY, 0xFF is transmitted from the module in response to a read sequence.

In addition to the clock stretch function, flow can also be controlled by monitoring the SBUSY signal. SBUSY signal changes according to the receive buffer state. The host should send data when SBUSY=READY.

Data Write Sequence Frame

Data Read Sequence Frame

I2C Timing

Parameter Symbol Condition Min. Typ. Max. Unit
SCL clock frequency fSCL – 0 – 400 kHz
Start condition hold time tHD;STA – 0.6 – – µs
SCL ‘L’ time tLOW – 1.3 – – µs
SCL ‘H’ time tHIGH – 0.6 – – µs
Start condition setup time tSU;STA – 0.6 – – µs
Data hold time tHD;DAT – 0 – – µs
Data setup time tSU;DAT – 100 – – ns
SCL, SDA rise time tr – 20 – 300 ns
SCL, SDA fall time tf – – 300 ns
Stop condition setup time tSU;STO – 0.6 – – µs
Stop condition – start condition bus idle time tBUF – 20 – – µs

Data Write Sequence

Data Read Sequence