Philips TEA5880TS 8.4 Reading from the TEA5880TS, 8.5 Measuring frequency with the TEA5880TS

Preliminary data sheet Rev. 02 — 26 April 2004 14 of 27

Philips Semiconductors TEA5880TS

Integrated FM stereo radio IC for host processor tuning

8.4 Reading from the TEA5880TS

Only the status or the counter register can be read from the TEA5880TS.

These are 16-bit registers and can be read serially as follow:

1. Select OS_PISO (parallel in, serial out) as output (control register A,

OUTPUT_SELECT bits)

2. Clear the PISO (control register B, PISO_CLR bit, pulse HIGH-to-LOW transition)

3. Latch the counter register (control register B, L_CNT bit, pulse HIGH-to-LOW

transition) or the status register (control register B, L_STS bit, pulse HIGH-to-LOW

transition) into the PISO

4. Drive R/W pin LOW to set the TEA5880TS in output mode

5. Read the ﬁrst bit at pin DATA

6. Generate positive CLOCK pulse (LOW-to-HIGH transition)

7. Delay for a period of time to meet the data set-up time requirement

8. Read the data bit at pin DATA

9. Drive CLOCK into HIGH-to-LOW transition

10.Repeat step (6) to (9) 15 times to shift the remaining 15 bits of data out of the chip

Note: The TEA5880TS will shift the MSB out ﬁrst.

8.5 Measuring frequency with the TEA5880TS

The three frequencies: IF, stereo decoder clock and FM can be measured by using the

counter register and a software timing window. This is achieved as follows:

1. Select the output to be measured (control register A, OUTPUT_SELECT bits, select

OS_STEREO_DEC, OS_IF_OSC or OS_FM_OSC output)

2. Enable measure mode (clear EN_MEAS# bit of control register A)

3. Reset the counter (control register B, CNT_RST bit, pulse HIGH-to-LOW transition)

4. Start the counter on the TEA5880TS (control register B, set CNT1_EN bit); at the

moment the R/W signal goes LOW the counter starts

5. Wait time t

6. To stop the counter, ﬁrst set theR/W signal HIGH, then disable the counter in the

TEA5880TS (control register B, clear CNT1_EN bit)

7. Read the pulse count n from the counter register of the TEA5880TS

8. Restore the measure mode

9. Restore the output select bits.

Note: The measuring window begins at the moment the R/W signal is driven LOW (point

4) and ends when the R/W signal is driven HIGH (point 6).