QUAD PCM CODEC WITH
PROGRAMMABLE GAIN
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IDT821034
DESCRIPTION:
The IDT821034 is a single-chip, four channel PCM CODEC with on-
chip filters and programmable gain setting. This device provides both
µ-Law
and A-Law companding digital-to-analog and analog-to-digital
conversions based on ITU-T G.711 - G.714 specifications. The digital
filters in IDT821034 provides the necessary transmit and receive filtering
for voice telephone circuit to interface with time-division multiplexed
systems. The IDT821034 has a flexible PCM interface with software
selectable timing modes and independently programmable time slot for
each transmit and receive channel. It also integrates the SLIC signaling
functions through internal registers. The CODEC and SLIC control/status
registers are accessed via the Serial Control Interface.
The IDT821034 can be used in digital telecommunication applications
such as PBX, Central Office Switch, Digital Telephone and Integrated Voice/
Data Access Unit.
4 channel CODEC with on-chip digital filters
Software Selectable A-law/µ-law companding
Programmable gain setting
Automatic master clock frequency selection: 2.048MHz, 4.096
MHz or 8.192MHz
Flexible PCM interface with up to 128 programmable time slots,
data rate from 512 kbits/s to 8.192 Mbits/s
5 SLIC signaling pins per channel
Flexible Serial Control Interface to microcontroller
Software programmable timing modes
TTL and CMOS compatible digital I/O
Meets or exceeds ITU-T G.711 - G.714 requirements
+5 V single power supply
Low power consumption: 100mW Typ.
Operating temperature range: -40 °C to +85 °C
Packages available: 52 pin PQFP
FUNCTIONAL BLOCK DIAGRAM
GSX0
VFXI0
-
+
+2.5V
A/D
Channel 0
D/A
SLIC Interface I/O
Channel 1
Channel 2
Channel 3
DSP
PCM
Interface
DX
DR
FS
BCLK
TSX
VFRO0
O_0(4 - 2)
I/O_0(1 - 0)
Serial
Control
Interface
CO
CI
CS
CCLK
Timing
MCLK
The IDT logo is a registered trademark of Integrated Device Technology, Inc
INDUSTRIAL TEMPERATURE RANGE
1
©
2003 Integrated Device Technology, Inc.
MAY 13, 2003
DSC-6032/3
IDT821034 QUAD PCM CODEC WITH PROGRAMMABLE GAIN
INDUSTRIAL TEMPERATURE RANGE
PIN CONFIGURATIONS
VFRO0
I/O1_1
I/O1_0
I/O0_1
27
26
25
24
23
22
21
VFXI0
GSX0
O1_4
O1_3
O1_2
O0_4
30
O0_3
29
O0_2
28
CNF
36
39
38
37
35
34
33
32
GNDA
GNDA
VFXI1
GSX1
VFRO1
VDDA
GNDA
VDDA
VFRO2
GSX2
VFXI2
GNDA
GNDA
40
41
42
43
44
45
46
47
48
49
50
51
52
10
11
12
13
1
2
3
4
5
6
7
8
9
31
I/O0_0
GND
CS
CI
CO
CCLK
BCLK
MCLK
FS
TSX
DR
VDD
DX
52-Pin PQFP
20
19
18
17
16
15
14
GSX3
VFRO3
VFXI3
I/O2_1
I/O2_0
I/O3_1
PIN DESCRIPTION
Name
GNDA
Type
--
Pin Number
46
51
52
40
41
47
45
3
48
44
37
2
49
43
38
1
50
42
39
9
10
11
4
5
6
Description
Analog Ground.
All ground pins should be connected to the ground plane of the circuit board.
VDDA
VFRO3
VFRO2
VFRO1
VFRO0
GSX3
GSX2
GSX1
GSX0
VFXI3
VFXI2
VFXI1
VFXI0
O3_4
O3_3
O3_2
O2_4
O2_3
O2_2
--
O
+5 V Analog Power Supply.
This pin should be bypassed to ground using 0.1
µ
F capacitor. All power supply pins should be connected to
the power plane of the circuit board.
Voice Frequency Receiver Output.
This is the output of receive power amplifier. It can drive 2000
Ω
(or greater) load.
Gain Setting Transmit Amplifier Output.
This pin is the output of the gain setting amplifier, and the input to the differential transmit filter. It should be
connected to the corresponding VFXI pin through a resistive network to set the transmit gain. Refer to Figure
5 for details.
Voice Frequency Transmitter Input.
This pin is the input to the gain setting amplifier in the transmit path.
SLIC Signaling Output for Channel 3.
SLIC Signaling Output for Channel 2.
O
I
O
O
2
I/O3_0
O2_4
O2_3
O2_2
O3_4
O3_3
O3_2
IDT821034 QUAD PCM CODEC WITH PROGRAMMABLE GAIN
INDUSTRIAL TEMPERATURE RANGE
PIN DESCRIPTION (CONTINUED)
Name
O1_4
O1_3
O1_2
O0_4
O0_3
O0_2
I/O3_1
I/O3_0
I/O2_1
I/O2_0
I/O1_1
I/O1_0
I/O0_1
I/O0_0
DX
VDD
DR
TSX
FS
MCLK
BCLK
CCLK
CO
CI
CS
GND
CNF
Type
O
O
I/O
I/O
I/O
I/O
O
--
I
O
I
I
I
I
O
I
I
--
O
Pin Number
35
34
33
30
29
28
12
13
7
8
32
31
27
26
14
15
16
17
18
19
20
21
22
23
24
25
36
Description
SLIC Signaling Output for Channel 1.
SLIC Signaling Output for Channel 0.
SLIC Signaling I/O for Channel 3.
SLIC Signaling I/O for Channel 2.
SLIC Signaling I/O for Channel 1.
SLIC Signaling I/O for Channel 0.
Transmit PCM Data Output.
PCM data is shifted out of DX on rising edges of BCLK.
+5 V Digital Power Supply.
All power supply pins should be connected to the power plane of the circuit board.
Receive PCM Data Input.
PCM data is shifted into DR on falling edges of BCLK.
Time Slot Indicator Output, Open Drain
This pin pulses low during the active time slot of each channel. A low level on this pin indicates active DX
output.
Frame Synchronization.
The FS pulse serves as the reference to time slots. The width of the FS pulse should be at least one BCLK
cycle.
Master Clock.
Master Clock provides the clock for DSP. It can be 2.048 MHz, 4.096 MHz or 8.192 MHz. It must be
synchronous to FS.
Bit Clock.
Bit Clock shifts out PCM data on DX pin and shifts in PCM data on DR pin. The clock can vary from 512 kHz
to 8.192 MHz at 64 kHz increment, depending on the time slot requirement of the system.
Serial Control Interface Clock.
This is the clock for Serial Control Interface. It can be up to 8.192 MHz.
Serial Control Interface Data Tri-State Output.
This pin is used to monitor SLIC working status. It is in high impedance state when
CS
is high.
Serial Control Interface Data Input.
Data input on this pin can control both CODEC and SLIC.
Chip Select.
A low level on this pin enables the Serial Control Interface.
Ground.
All ground pins should be connected to the ground plane of the circuit board.
Capacitor For Noise Filter.
This pin should be connected to GNDA via a 0.1
µ
F capacitor.
3
IDT821034 QUAD PCM CODEC WITH PROGRAMMABLE GAIN
INDUSTRIAL TEMPERATURE RANGE
FUNCTIONAL DESCRIPTION
The IDT821034 contains four channel PCM CODEC with on chip digital
filters. It provides the four-wire solution for the subscriber line circuitry in
digital switches. The device converts analog voice signal into digital PCM
samples, and converts digital PCM samples back to analog signal. Digital
filters are used to bandlimit the voice signals during conversion.
The frequency of the master clock (MCLK) can be 2.048 MHz, 4.096
MHz or 8.192 MHz. Internal circuitry determines the master clock frequency
automatically.
Four channels of serial PCM data are time multiplexed via two pins, DX
and DR. The time slots of the four channels can be programmed
dynamically. The control words can be written by a microcontroller via the
Serial Control Interface. Dynamic time-slot assignment can accommodate
8 to 128 time slots corresponding to the bit clock (BCLK) frequency from
512 kHz to 8.192 MHz.
The IDT821034 offers two timing modes, delay mode and non-delay
mode. Mode selection is done by programming the Configuration Register.
The two modes are distinguished by time slot zero definition. In delay
mode, the time slot zero is defined as starting on the first rising edge of
BCLK after FS = ‘1’ is detected by the falling edge of BCLK (Figure 7).
While in non-delay mode, the time slot zero starts when both BCLK and
FS are high (Figure 8).
The device provides a programmable interface to SLIC (Subscriber Line
Interface Circuit). Each channel of the IDT821034 has three output pins
and two I/O pins for SLIC signaling. These interface pins are mapped to
internal registers and are accessed by the microcontroller via the Serial
Control Interface. In this way, the IDT821034 provides high level of
integration in line card design.
The Serial Control Interface of IDT821034 consists of four pins (CI,
CO,
CS
and CCLK), as shown in Figure 1, for the communication to a
microcontroller. Via this interface, the microcontroller can control the
CODEC and SLIC working modes as well as monitor the SLIC status.
information retain the data in this mode.
Each of the four channels in the IDT821034 can be in either normal
mode or standby mode. The mode selection of each channel is done by
the microcontroller via the Serial Control Interface. When in normal mode,
each channel of the IDT821034 is able to transmit and receive both PCM
and analog information. This is the operating mode when a telephone call
is in progress.
Gain Programming
Transmit gain and receive gain of each channel in IDT821034 can be
varied by programming DSP digital filter coefficients. Transmit gain can be
varied within the range of -3 dB to +13 dB; while receive gain can be
varied within the range of -13 dB to +3 dB. This function
allows the
IDT821034 to be used with SLICs of different gain requirement.
OPERATION CONTROL
Gain programming coefficient can be written into IDT821034 via Serial
Control Interface. The detailed operation will be covered in Serial Control
Interface description. The gain programming coefficients should be
calculated as:
Transmit : Coeff_X = round [ gain_X0dB × gain_X ]
Receive: Coeff_R = round [ gain_R0dB × gain_R ]
where:
gain_X0dB = 1820;
gain_X is the target gain;
Coeff_X should be in the range of 0 to 8192.
gain_R0dB = 2506;
gain_R is the target gain;
Coeff_R should be in the range of 0 to 8192.
A gain programming coefficient is 14-bit wide and in binary format. The
7 Most Significant Bits of the coefficient is called GA_MSB_Transmit for
transmit path, or is called GA_MSB_Receive for receive path; The 7 Least
Significant Bits of the coefficient is called GA_LSB_ Transmit for transmit
path, or is called GA_LSB_Receive for receive path.
An example is given below to clarify the calculation of the coefficient. To
program a +3 dB gain in transmit path and a -3.5 dB gain in receive path:
Linear Code of +3 dB
The following operation description applies to all four channels of the
IDT821034.
Initial State
The IDT821034 has a built-in power on reset circuit. After initial power
up, the device defaults to the following mode:
1. A-law is selected;
2. Delay mode is selected;
3. I/O pins of SLIC interface are set to input mode;
4. SLIC Control and Status Register bits are set to ‘0’;
5. All four channels are placed in standby mode;
6. All transmit and receive time slots are disabled with Time Slot Reg-
isters set to zero;
7. DX is set to high impedance state.
Operating Modes
There are two operating modes for each transmit or receive channel:
standby mode and normal mode. When the IDT821034 is first powered
on, standby mode is the default mode. Microcontroller can also set the
device into this mode via the Serial Control Interface. In standby mode, the
Serial Control Interface remains active to receive commands from the
microcontroller. All other circuits are powered down with the analog outputs
placed in high impedance state. All circuits which contain programmed
4
= 10
3/20
= 1.412537545
= round (1820 × 1.412537545)
= 2571
= 0010100, 0001011
(in binary format )
= 0010100
= 0001011
Coeff_X
GA_MSB_Transmit
GA_LSB_Transmit
Linear Code of -3.5 dB = 10
(-3.5/20)
= 0.668343917
Coeff_R
= round (2506 × 0.668343917)
= 1675
= 0001101, 0001011
(in binary format)
= 0001101
= 0001011
GA_MSB_Receive
GA_LSB_Receive
IDT821034 QUAD PCM CODEC WITH PROGRAMMABLE GAIN
INDUSTRIAL TEMPERATURE RANGE
SIGNAL PROCESSING
High performance oversampling Analog-to-Digital Converters (ADC) and
Digital-to-Analog Converters (DAC) are used in the IDT821034 to provide
the required conversion accuracy. The associated decimation and inter-
polation filters are realized with both dedicated hardware and Digital Sig-
nal Processor (DSP). The DSP also handles all other necessary functions
such as PCM bandpass filtering and sample rate conversion.
Transmit Signal Processing
In the transmit path, the analog input signal is received with a gain
setting amplifier. The signal gain is set by the resistive feedback network
as shown in the application circuit (Figure 5). The output of the gain
setting amplifier is connected internally to the input of the anti-alias filter
for the oversampling ADC. The digital output of the oversampling ADC
is decimated and sent to the DSP. The transmit filter is implemented in
the DSP as a digital bandpass filter. The filtered signal is further decimated
and compressed to PCM format.
Transmit PCM Interface
The transmit PCM interface clocks the PCM data out of DX pin on rising
edges of BCLK according to the time slot assignment. The frame sync
(FS) pulse identifies the beginning of a transmit frame, or time slot zero.
The time slots for all channels are referenced to FS. The IDT821034
contains user programmable Transmit Time Slot Register for each transmit
channel. The register is 7 bits wide and can accommodate up to 128 time
slots (corresponding to the maximum BCLK frequency of 8.192 MHz) in
each frame. The PCM Data is transmitted serially on DX pin with the Most
Significant Bit (MSB), or Bit 7, first.
When the device is first powered up, all transmit time slots are disabled
with Transmit Time Slot Registers set to zero. DX pin remains in high-
impedance state. To power up or power down each transmit channel,
Configuration Register and the corresponding Time Slot Register must be
programmed.
Receive Signal Processing
In the receive path, the PCM code is received at the rate of 8,000
samples per second. The PCM code is expanded and sent to the DSP
for interpolation and receive channel filtering function. The receive filter
is implemented in the DSP as a digital lowpass filter. The filtered signal
is then sent to an oversampling DAC. The DAC output is post-filtered
and then delivered at VFRO pin by a power amplifier. The amplifier can
drive resistive load higher than 2 kΩ.
Receive PCM Interface
The receive PCM interface clocks the PCM data into DR pin on falling
edges of BCLK according to the time slot assignment. The receive time
slot definition and programming is similar to that of the transmit time slot.
The IDT821034 contains a user programmable Receive Time Slot Register
for each receive channel. The register is 7 bits wide and can accommodate
up to 128 time slots (corresponding to the maximum BCLK frequency of
8.192 MHz) in each frame. The PCM Data is received serially on DR pin
with the MSB (Bit 7) first.
When the device is first powered up, all receive time slots are disabled
with Receive Time Slot Registers set to zero. Data on DR pin is ignored. To
power up or power down each receive channel, Configuration Register
and the corresponding Time Slot Register must be programmed.
Serial Control Interface
A Serial Control Interface is provided for a microprocessor to access
the control and status registers of IDT821034. The control registers include
Configuration Register, Time Slot Registers, SLIC Control Registers and
Gain Adjustment Registers. They are used to program the working modes
of CODEC and SLIC. The status registers include SLIC Status Registers.
They are used to monitor SLIC functions. All registers are 8 bits wide.
The Serial Control Interface consists of CO, CI,
CS
and CCLK pins
(see Figure 1). A microprocessor initiates a write or read cycle after low
level is asserted on
CS
pin. In the microprocessor write cycle, 8 bits of
serial data on CI pin are shifted into the device at falling edges of CCLK.
In the microprocessor read cycle, 8 bits of serial data are shifted out of
the device on CO pin at rising edges of CCLK. At the end of each 8-bit
transaction, the microprocessor sets
CS
high to terminate the cycle.
Multiple accesses to the device are separated by an idle state (high
level) of
CS.
The width of
CS
high level is at least three CCLK cycles.
The IDT821034 has a Configuration Register. Its register bits are
designated CR.7 - CR.0. The definition of the bits in Configuration Register
is shown in Table 1. If the leading data bit on CI pin is ‘1’ in a
microprocessor write cycle, the 8-bit data on CI pin is latched into
Configuration Register with MSB first.
There are eight Time Slot Registers for four transmit channels and
four receive channels. The definition of the bits in Time Slot Register is
shown in Table 2. Since PCM sample rate is 8k samples/sec and each
sample is 8 bits wide, each time slot occupies 64 kbits/sec of data rate.
The number of time slots in a frame is equal to the ratio of the bit
clock frequency (BCLK) to 64 kHz. For the maximum BCLK frequency
of 8.192 MHz, the number of time slots in a frame is 8.192MHz/64kHz,
or 128. The minimum number of time slots (corresponding to the
minimum BCLK frequency of 512 kHz) in a frame is 8. The relationship
between frequently used BCLK frequencies and the number of time slots
in a frame is shown in Table 3. Bit 6-0 in each Time Slot Register identify
the time slot number (0 to 127) of the corresponding transmit or receive
channel. Time Slot Registers can be accessed by specifying the transmit/
receive select (CR.1 and CR.0) and channel address (CR.3 and CR.2)
in Configuration Register. If CR.6 = ‘0’ and the leading data bit on CI pin
is ‘0’ in a microprocessor write cycle, the 8-bit data on CI pin is latched
into the selected Time Slot Register with MSB first.
There are four SLIC Control Registers for four channel SLIC signaling
control. The definition of the bits in a SLIC Control Register is shown in
Table 4. SLIC Control Registers can be accessed by specifying the
channel address (CR.3 and CR.2) in Configuration Register. If CR[6:4] =
‘101’ and the leading data bit on CI pin is ‘0’ in a microprocessor write or
read cycle, the 8-bit data on CI pin is latched into the selected SLIC
Control Register with MSB first.
There are four SLIC Status Registers for four channel SLIC monitoring.
The bits in each SLIC Status Register are mapped to the SLIC signaling
output and I/O pins of the corresponding channel as shown in Table 5. It
should be noted that the last 3 bits of the SLIC Status Register are always
mapped to I/O1_0, I/O2_0 and I/O3_0. This feature allows a rapid read
process of the SLIC status when Channel 0 is selected. The SLIC Status
Registers can be accessed by specifying the channel address (CR.3
and CR.2) in the Configuration Register. If CR[6:4] = ‘101’, as a result of
the previous write to the Configuration Register, the subsequent
microprocessor cycle is a read cycle. The content of the selected SLIC
Status Register is shifted out of the device on CO pin with MSB first.
There are 16 Gain Adjustment Registers for both transmit and
receive paths of four channels. For each path, there are two
5
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