NEC Diamond Scan 51, Service Manual

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(5) Data bytes transmit/receive
If the RW bit is “1”, the shift register will load data from the data buffer (REG#18H) before the data byte
is transmitted and shift out data to the SDA pin before the rising edge of the SCL clock.
If the RW bit is “0”, the shift register will shift in data on the rising edge of the SCL clock and the whole
data byte is latched to the data buffer (REG#18H).
(6) Handshaking procedure
The handshaking is done on the byte level. The DDC interface will hold the SCL pin low after the ac-
knowledge bit automatically. The bus master will be forced to wait until the WT6018 is ready for the next
byte transfer. To release the SCL pin, write REG#19H will release clear the wait state.
(7) Interrupt INT0
The DDC interface interrupt is enabled by setting the IEN_D bit in the REG#1AH.
Interrupt INT0 occurs when:
-
Transmit buffer empty in DDC1 state.
The INT0 occurs when the shift register load data from data buffer.
Write REG#18H will clear the transmit buffer empty condition.
-
Acknowledge is detected in DDC2B state.
The INT0 occurs on the falling edge of the SCL clock after the acknowledge had been detected.
The SCL pin will be pulled low to force the bus master to wait until the service routine write
REG#19H.
-
STOP condition occurs in DDC2B mode
Address R/W Initial Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
0018H R/W FFH D7 D6 D5 D4 D3 D2 D1 D0
0019H R 40H DDC2B ADDR R/W START STOP -- -- --
0019H W A0H A6 A5 A4 A3 A2 A1 A0 ENACK
Bit Name Bit value = “1” Bit value = “0”
DDC2B DDC2B state. DDC1 state.
ADDR
Received address equals to the address
in REG#19H(W).
Received address equals to ‘1010000’
RW Received R/W bit is ‘1’ Received R/W bit is ‘0’
START START condition is detected. No START condition is detected.
STOP STOP condition is detected. No STOP condition is detected.
ENACK Enable acknowledge. Disable acknowledge.
A6, A5, … , A0 7-bit slave address
D7, D6, … , D0 Data to be transmitted or received data.
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