ST72774/ST727754/ST72734
110/144
DDC INTERFACE (Cont’d)
4.8.6 Register Description
DDC CONTROL REGISTER (CR)
Read / Write
Reset Value: 0000 0000 (00h)
Bit 7:6 = Reserved. Forced to 0 by hardware.
Bit 5 = PE
Peripheral enable.
This bit is set and cleared by software.
0: Peripheral disabled
1: Slave capability
Notes:
– When PE=0, all the bits of the CR register and
the SR register are reset. All outputs are re-
leased while PE=0
– When PE=1, the corresponding I/O pins are se-
lected by hardware as alternate functions.
– To enable the I2C interface, write the CR register
TWICE with PE=1 as the first write only activates
the interface (only PE is set).
Bit 4 = EDDCEN
Enhanced DDC address
detection enabled.
This bit is set and cleared by software. It is also
cleared by hardware when the interface is disabled
(PE=0). The 60h/61h Enhanced DDC address is
acknowledged.
0: Enhanced DDC address detection disabled
1: Enhanced DDC address detection enabled
Bit 3 = Reserved. Forced to 0 by hardware.
Bit 2 = ACK
Acknowledge enable.
This bit is set and cleared by software. It is also
cleared by hardware when the interface is disabled
(PE=0).
0: No acknowledge returned
1: Acknowledge returned after an address byte or
a data byte is received
Bit 1 = STOP
Release I2C bus.
This bit is set and cleared by software or when the
interface is disabled (PE=0).
– Slave Mode:
0: Nothing
1: Release the SCL and SDA lines after the cur-
rent byte transfer (BTF=1). The STOP bit has to
be cleared by software.
Bit 0 = ITE
Interrupt enable.
This bit is set and cleared by software and cleared
by hardware when the interface is disabled
(PE=0).
0: Interrupts disabled
1: Interrupts enabled
Refer to Figure 68 for the relationship between the
events and the interrupt.
SCL is held low when the BTF or ADSL is detect-
ed.
70
00
PE
EDDC
EN
0ACK
STOP
ITE