TDA9950_2

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 02 — 22 October 2009

8 of 22

NXP Semiconductors

TDA9950

8.5 Data register protocol

Communication between the TDA9950 and the host using the CEC Data Registers is

carried out using frames of information. The host is the master of all data transfers; the

TDA9950 uses the INT line to inform the host that it has data available.

Before a frame is read or written, the host must set the REG_PTR field in the Address

Pointer Register to the base CEC Data Register address. Successive reads or writes

automatically increment the REG_PTR as the frame is transferred. Message transfers can

only start from the first CEC Data Register at address 07h and not from higher addresses,

as messages must be transferred complete and not in fragments.

Each frame consists of a byte count, a service selector and then zero or more (up to 17)

parameters as shown in Figure 3.

The FrameByteCount indicates the number of bytes in the frame (including the

FrameByteCount itself). The service is specified by the ServiceSelector (see Table 15).

The remaining bytes of the frame, if any, contain the parameters associated with a

particular service. The maximum length of a frame is 19 bytes. The TDA9950 will only

accept a single outstanding request. Reading message bytes beyond FrameByteCount

will return FFh.

Table 15 shows the organization of the ServiceSelector values. If an unused

ServiceSelector is sent to the TDA9950 it will respond with the confirmation Bad .req

service (see Table 17). For every service, the parameters that are defined in the following

sections are mandatory. No service contains optional parameters.

4

ENABLE_ERROR

ENABLE_ERROR:

0 = no specific action.

1 = notify the host of all errors via the TDA9950 Error Register

and via the CECData.err service (see Section 8.5.4).

3

-

not used

2 to 0

RETRY[2:0]

RETRY[2:0]: retry count to be used by the TDA9950. The

maximum value is 5; values greater than 5 will still give 5

retries.

Table 14.

CDR[0:18] - CEC Data Registers (addresses 07h to 19h) bit description

(Read/Write)

Bit

Symbol

Description

7 to 0

FrameByteCount/

ServiceSelector/

Parameters[7:0]

FrameByteCount/ServiceSelector/Parameters:

Length of message in B, Type of message, 17 B for message

content; see Section 8.5 “Data register protocol”.

Table 13.

CCONR - CEC Configuration Register (address 06h) bit description (Read/Write)

Bit

Symbol

Description

Fig 3.

Frame format for the data register protocol

001aag924

FrameByteCount

ServiceSelector

[Parameters]

Register CDR0

Register CDR1

Register CDR2

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