McASP
Encyclopedia
McASP is an acronym for Multichannel Audio Serial Port, a communication peripheral found in Texas Instruments
family of digital signal processors (DSPs
).
The McASP functions as a general-purpose audio serial port optimized for the needs of multichannel audio applications.
The McASP is useful for time-division multiplexed (TDM
) stream, Inter-Integrated Sound (I2S) protocols, and intercomponent digital audio interface transmission (DIT).
The McASP consists of transmit and receive sections that may operate synchronized,
or completely independently with separate master clocks, bit clocks, and frame syncs,
and using different transmit modes with different bit-stream formats. The McASP
module also includes up to 16 serializers that can be individually enabled to either
transmit or receive. In addition, all of the McASP pins can be configured as
general-purpose input/output (GPIO
) pins.
The transmit and receive sections may each be individually programmed to support the following options
on the basic serial protocol:
In DIT mode, additional features of the transmitter are:
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
family of digital signal processors (DSPs
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
).
The McASP functions as a general-purpose audio serial port optimized for the needs of multichannel audio applications.
The McASP is useful for time-division multiplexed (TDM
Time-division multiplexing
Time-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
) stream, Inter-Integrated Sound (I2S) protocols, and intercomponent digital audio interface transmission (DIT).
The McASP consists of transmit and receive sections that may operate synchronized,
or completely independently with separate master clocks, bit clocks, and frame syncs,
and using different transmit modes with different bit-stream formats. The McASP
module also includes up to 16 serializers that can be individually enabled to either
transmit or receive. In addition, all of the McASP pins can be configured as
general-purpose input/output (GPIO
GPIO
General Purpose Input/Output is a generic pin on a chip whose behavior can be controlled through software....
) pins.
Features
Features of the McASP include:- Two independent clock generator modules for transmit and receive
- Clocking flexibility allows the McASP to receive and transmit at different rates. For example, the McASP can receive data at 48 kHz but output up-sampled data at 96 kHz or 192 kHz.
- Independent transmit and receive modules, each includes:
- Programmable clock and frame sync generator
- TDM streams from 2 to 32, and 384 time slots
- Support for time slot sizes of 8, 12, 16, 20, 24, 28, and 32 bits
- Data formatter for bit manipulation
- Individually assignable serial data pins (up to 16 pins)
- Glueless connection to audio analog-to-digital converters (ADCAnalog-to-digital converterAn analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
), digital-to-analog converters (DACDigital-to-analog converterIn electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
), CodecCodecA codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
, digital audio interface receiver (DIR), and S/PDIFS/PDIFS/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
transmit physical layer components. - Wide variety of I2S and similar bit-stream format
- Integrated digital audio interface transmitter (DIT) supports:
- S/PDIFS/PDIFS/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
, IEC60958-1, AES-3 formats - Up to 16 transmit pins
- Enhanced channel status/user data RAMRam-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
- S/PDIF
- 384-slot TDMTime-division multiplexingTime-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
with external digital audio interface receiver (DIR) device- For DIR reception, an external DIR receiver integrated circuit should be used with I2S output format and connected to the McASP receive section.
- Extensive error checking and recovery
- Transmit underruns and receiver overruns due to the system not meeting real-time requirements
- Early or late frame sync in TDM mode
- Out-of-range high-frequency master clock for both transmit and receive
- External error signal coming into the AMUTEIN input
- DMADirect memory accessDirect memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
error due to incorrect programming
Protocols
The McASP supports a wide variety of protocols.- Transmit section supports
- Wide variety of I2S and similar bit-stream formats
- TDM streams from 2 to 32 time slots
- S/PDIFS/PDIFS/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
, IEC60958-1, AES-3 formats
- Receive section supports
- Wide variety of I2S and similar bit-stream formats
- TDMTime-division multiplexingTime-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
streams from 2 to 32 time slots - TDMTime-division multiplexingTime-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
stream of 384 time slots specifically designed for easy interface to external digital interface receiver (DIR) device transmitting DIR frames to McASP using the I2S protocol (one time slot for each DIR subframe)
The transmit and receive sections may each be individually programmed to support the following options
on the basic serial protocol:
- Programmable clock and frame sync polarity (rising or falling edge): ACLKR/X, AHCLKR/X and AFSR/X
- Slot length (number of bits per time slot): 8, 12, 16, 20, 24, 28, 32 bits supported
- Word length (bits per word): 8, 12, 16, 20, 24, 28, 32 bits; always less than or equal to the time slot length
- First-bit data delay: 0, 1, 2 bit clocks
- Left/right alignment of word inside slot
- Bit order: MSBMost significant bitIn computing, the most significant bit is the bit position in a binary number having the greatest value...
first or LSBLeast significant bitIn computing, the least significant bit is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The lsb is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digits...
first - Bit mask/pad/rotate function
- Automatically aligns data for DSP internally in either Q31 or integer formats
- Automatically masks nonsignificant bits (sets to 0, 1, or extends value of another bit)
In DIT mode, additional features of the transmitter are:
- Transmit-only mode- 384 time slots (subframe) per frame
- Bi-phase encoded 3.3 V output
- Support for consumer and professional applications
- Channel status RAMRam-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
(384 bits) - User data RAMRam-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
(384 bits) - Separate valid bit (V) for subframe A, B