u4091bm-r ATMEL Corporation, u4091bm-r Datasheet - Page 8

• Manufacturer Part Number: u4091bm-r
• Description: Programmable Telephone Audio Processor
• Manufacturer: ATMEL Corporation

7. Clock Output Divider Adjustment
8. Serial Bus Interface
8.1
8.2
8
WRITE
READ
U4091BM-R
Table 6-1.
The pin OSCOUT is a clock output which is derived from the crystal oscillator. It can be used to
drive a microcontroller or another remote component and thereby reduces the number of crys-
tals required. The oscillator frequency can be divided by 1, 8, 16, or 32. During power-on reset,
the divider will be reset to 1 until it is changed by setting the serial bus.
Table 7-1.
The circuit is controlled by an external microcontroller through the serial bus.
The serial bus is a bi-directional system consisting of a single-directional clock line (SCL) which
is always driven by the microcontroller, and a bi-directional data-signal line. It is driven by the
microcontroller as well as by the U4091BM-R (see
The serial bus requires external pull-up resistors as only pull-down transistors (pin SDA) are
integrated.
The data is a 12-bit word:
A0-A3: address of the destination register (0 to 15)
D0-D7: content of the register
The data line must be stable when the clock is high. Data must be shifted serially. After 12 clock
periods, the write indication is sent. Then, the transfer to the destination register is (internally)
generated by a strobe signal transition of the data line when the clock is high.
There is a normal and a fast-read cycle.
In the normal read cycle, the microcontroller sends a 4-bit address followed by the read indica-
tor, then an 8-bit word is read out. The U4091BM-R drives the data line.
The fast read cycle is indicated by a strobe signal. With the following two clocks the U4091BM-R
reads out the status bits RFDO and LIDET which indicate that a ringing signal or a line signal is
present (see
CLK[0:1]
Figure 10-1 on page
Threshold Level
Clock Output
0
1
2
3
RINGTH[0:3]
Step
15
0
11,
Figure 10-2 on page 11
Divider
16
32
1
8
Figure 20-1 on page
and
Figure 10-3 on page
V
22V
7V
1V
RING
37).
Frequency
3.58 MHz
447 kHz
224 kHz
112 kHz
4872A–CORD–08/05
11).