RM0444 Rev 5 1357/1390
RM0444 HDMI-CEC controller (CEC)
1364
39.7 HDMI-CEC registers
Refer to Section 1.2 on page 53 for a list of abbreviations used in register descriptions.
39.7.1 CEC control register (CEC_CR)
Address offset: 0x00
Reset value: 0x0000 0000
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res.
1514131211109876543210
Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res. Res.
TXE
OM
TXS
OM
CECEN
rs rs rw
Bits 31:3 Reserved, must be kept at reset value.
Bit 2 TXEOM: Tx end of message
The TXEOM bit is set by software to command transmission of the last byte of a CEC message.
TXEOM is cleared by hardware at the same time and under the same conditions as for TXSOM.
0: TXDR data byte is transmitted with EOM = 0
1: TXDR data byte is transmitted with EOM = 1
Note: TXEOM must be set when CECEN = 1.
TXEOM must be set before writing transmission data to TXDR.
If TXEOM is set when TXSOM = 0, transmitted message consists of 1 byte (HEADER) only
(PING message).
Bit 1 TXSOM: Tx start of message
TXSOM is set by software to command transmission of the first byte of a CEC message. If the CEC
message consists of only one byte, TXEOM must be set before of TXSOM.
Start-bit is effectively started on the CEC line after SFT is counted. If TXSOM is set while a message
reception is ongoing, transmission starts after the end of reception.
TXSOM is cleared by hardware after the last byte of the message is sent with a positive
acknowledge (TXEND = 1), in case of transmission underrun (TXUDR = 1), negative acknowledge
(TXACKE = 1), and transmission error (TXERR = 1). It is also cleared by CECEN = 0. It is not
cleared and transmission is automatically retried in case of arbitration lost (ARBLST = 1).
TXSOM can be also used as a status bit informing application whether any transmission request is
pending or under execution. The application can abort a transmission request at any time by
clearing the CECEN bit.
0: No CEC transmission is on-going
1: CEC transmission command
Note: TXSOM must be set when CECEN = 1.
TXSOM must be set when transmission data is available into TXDR.
HEADER first four bits containing own peripheral address are taken from TXDR[7:4], not from
CEC_CFGR.OAR that is used only for reception.
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