
S3C8639/C863A/P863A/C8647/F8647
DDC MODULE
17-3
DDC Clock Control Register (DCCR)
The DDC clock control register, DCCR, is located at EBH in set 1, bank 1. It is read/write addressable. DCCR
settings control the following functions:
— CPU acknowledge signal (ACK) enable or suppress
— DDC clock source selection (f
OSC/10 or fOSC/256)
— DDC interrupt enable or disable
— DDC interrupt pending control
— 4-bit prescaler for the serial clock (SCL0)
When DCCR.7 bit is set to "1", it is enable to acknowledgment signal. DCCR.6 is bit for transmit clock source
selection by f
OSC/10 or fOSC/256. DCCR.3–DCCR.0 bits (CCR3–CCR0) are 4-bit prescaler for the transmit clock
(SCL0). The SCL0 clock may be "Stretched" if a slow slave device holds the clock for clock synchronization.
In the S3C8639/C863A/C8647 interrupt structure, the DDC interrupt is assigned level IRQ3, vector EAH. To
enable this interrupt, you set DCCR.5 to "1". Program software can then poll the DDC interrupt pending
bit(DCCR.4) to detect DDC interrupt request. When the CPU acknowledges the interrupt request from the DDC,
the interrupt service routine must clear the interrupt pending condition by writing a "0" to DCCR.4.
DDC Clock Control Register (DCCR)
EBH, Set 1, Bank 1, R/W
.7
.6
.5
.4
.3
.2
.1
.0
MSB
LSB
Transmit clock 4-bit prescaler bits:
The transmit clock (SCL0) frequency is
determined by the clock source selection
(DCCR.6) and this 4-bit prescaler
value, according to the following formula:
SCL0 clock = IICCLK/(DCCR.3-DCCR.0) + 1
where, IICCLK is fOSC/10 (DCCR.6 = "0") or
IICCLK is fOSC/256 (DCCR.6 = "1")
Transmit acknowledge (ACK)
enable bit:
0 = Disable ACK generation
1 = Enable ACK generation
Transmit clock source selection bit:
0 = fOSC/10
1 = fOSC/256
DDC module interrupt enable bit:
0 = Disable DDC interrupt
1 = Enable DDC interrupt
DDC module interrupt pending flag:
0 = When write "0" to this bit (write "1" has no effect)
0 = When DCSR0.4 is "0"
1 = When slave address match occurred
1 = When arbitration lost (master mode)
1 = When a 1-byte transmit or receive operation is terminated
1 = As soon as the DDC1 mode is enable after the prebuffer is used
Figure 17-2. DDC Clock Control Register (DCCR)