Datasheet

TEF6901A_3 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 03 — 20 March 2008 21 of 107
NXP Semiconductors
TEF6901A
Integrated car radio
8.1.7 Read mode: data byte TEMP
8.2 Write mode
The device is controlled by the I
2
C-bus. After the Integrated Circuit (IC) address the MSA
byte contains the control of the tuning action via the bits MODE[2:0] and subaddressing
via bits SA[4:0] (see Figure 8).
All circuits are controlled by the CONTROL register. Any data change in the CONTROL
register has immediate effect and will change the operation of the circuit accordingly. The
subaddress range 00h to 05h includes data that may lead to audible disturbance when
changed. Therefore the subaddress range 00h to 05h is not loaded in the CONTROL
register directly but loaded in a BUFFER register instead. This allows the IC to take care
of tuning actions and mute control, freeing the microcontroller from cumbersome controls
and timings. The subaddress range of 06h onwards does not contain such critical data.
I
2
C-bus information in this range will be loaded in the CONTROL register directly (at
acknowledge of each byte).
Controlled by a state machine the BUFFER data will be loaded in the CONTROL register
for new settings. However at the same time the CONTROL data is loaded in the BUFFER
register. This register swap action allows a fast return to the previous setting because the
previous data remains available in the BUFFER register (see Figure 10, Figure 11 and
Figure 12).
Via MODE several operational modes can be selected for the state machine. MODE offers
all standard tuning actions as well as generic control for flexibility. The state machine
controls the tuner directly by controlling the I
2
C-bus data. Internal circuits like the IF
counter, mute and weak signal processing are controlled complementary to the tuner
action. The state machine operation starts at the end of transmission (P = STOP). In case
a previous action is still active this is overruled and the new action defined by MODE is
started immediately.
When only the address byte is transmitted no action is started and no setting is changed,
this can be used to test the presence of the device on the bus. To minimize the I
2
C-bus
transmission time only bytes that include data changes need to be written. Following the
MSA byte the transmission can start at any given data byte defined by the subaddress
(SA) bits. In case of MODE = preset, search or load the value of buffered data that is not
overwritten by the new transmission will equal the control register content, i.e. the current
tuner state. Instead in case of MODE = buffer, AF update, jump, check or end any not
overwritten BUFFER data remains to be the existing BUFFER register content, i.e. the
previous tuner state.
Table 20. TEMP - format of data byte 6
7 6 5 4 3 2 1 0
TEMP7 TEMP6 TEMP5 TEMP4 TEMP3 TEMP2 TEMP1 TEMP0
Table 21. TEMP - data byte 6 bit description
Bit Symbol Description
7 to 0 TEMP[7:0] on-chip temperature; 1 step ≈ 1 K; relative indication