Hdmi-Cec Functional Description; Hdmi-Cec Pin; Table 102. Hdmi Pin; Figure 289. Block Diagram - STMicroelectronics STM32F05 series Reference Manual

HDMI-CEC controller (HDMI-CEC)
28.3

HDMI-CEC functional description

28.3.1

HDMI-CEC pin

The CEC bus consists of a single bidirectional line that is used to transfer data in and out of
the device. It is connected to a +3.3 V supply voltage via a 27 kΩ pull-up resistor. The output
stage of the device must have an open-drain or open-collector to allow a wired-and
connection.
The HDMI-CEC controller manages the CEC bidirectional line as an alternate function of a
standard GPI/O, assuming that it is configured as Alternate Function Open Drain. The 27 kΩ
pull-up must be added externally to the STM32.
To not interfere with the CEC bus when the application power is removed, it is mandatory to
isolate the CEC pin from the bus in such conditions. This could be done by using a MOS
transistor, as shown on

Table 102. HDMI pin

Name
CEC

Figure 289. Block diagram

Cortex-M0
HSI/255
LSE
1. GPI/O configured as output open-drain alternate function
2. When configured as output open-drain alternate function, the schmit trigger is still activated.
700/742
Figure 289.
Signal type
bidirectional
CEC interrupt
CEC
ITF
APB
AHB
RCC clk
32 kHz
CEC
Kernel
Event
control
Wake-int
Doc ID 018940 Rev 1
two states:
1 = high impedance
0 = low impedance
kΩ
A 27 must be added externally.
STM32
HDMI_CEC
controller
27
Rx
CEC
Tx
PAD(*)
RM0091
Remarks
3.3V
3.3V
G
Remote
CEC line S D
MS19885V2
CEC
device