Intel STRONGARM SA-1100 - Manual (Page 300)

11-150 SA-1100 Developer’s Manual
Peripheral Control Module
The width of each entry within the audio and telecom FIFOs is 16 bits. However, the audio codec’s
sample/conversion data size is 12 bits and the telecom is 14 bits. Conversions and samples are left
justified within the 16-bit audio and telecom data fields in the MCP frame as well as within the
transmit and receive FIFOs.
Figure 11-34 shows the required data alignment for the transmit and
receive audio and telecom FIFOs. The user must left justify data to be transmitted, and shift
received data to the right before using the results.
Figure 11-34. Audio/Telecom Transmit/Receive FIFO Data Format
To reduce chip size as well as power consumption, the MCP’s FIFOs use self-timed logic (not
clocked). Because of process and environmental variations, the depth at which a service request is
triggered to empty the receive FIFOs is variable. This variation spans a maximum of four FIFO
entries, thus the audio and telecom receive FIFO service requests can be made at four different
FIFO depths.To compensate for this variability and guarantee that at least four valid entries of data
exist within either FIFO before generating a service request, an extra four entries have been added
to both receive FIFOs (four entries more than the transmit FIFOs). Thus the audio and telecom
transmit FIFOs are 8-entries deep and the audio and telecom receive FIFOs are 12-entries deep.
The point at which the receive FIFO service requests are triggered spans one-third (four entries) of
the 12-entry FIFOs. The service request is signalled at a depth from one-third full to two-thirds full
(when the FIFOs contains five, six, seven, or eight entries of data).
11.12.1.4 Codec Control Register Data Transfer
The UCB1100 and UCB1200 contain sixteen 16-bit registers used to configure the chip, and store
touch-screen and ADC samples as well as digital I/O pin state and edge interrupt status. These
registers are read and written via the MCP’s serial interface using three fields that exist within the
MCP’s data frame. In
Figure 11-31 , bits 15:0 contain the value read from or written to the off-chip
codec, bits 46:43 contain the register address of the current read or write, and bit 42 is used by the
MCP to signal a read or write cycle to the codec. These fields are configured by the CPU by writing
to MCP control register 2, and are then transmitted to the off-chip codec. These fields are also
received every data frame by the MCP from the codec and are placed in MCP control register 2,
which can be read by the CPU. Note that the contents of the addressed register are returned in the
receive data frame regardless of the state of the read/write bit. Thus for write cycles, both a write
and a read occurs, and for read cycles, only a read occurs.
A register write is performed by writing a value to the MCP control register 2 that contains the
value to store to the register, the address of the register, and the read/write bit set to one. Once this
register is written, its contents are transferred to the correct fields within the serial shifter on the
next rising edge of the SFRM signal. The register information is transmitted to the UCB1100 or
UCB1200 during subframe 0, and the value is written to the selected codec register at the end of
subframe 0 (during the 65th bit of the frame). The control register value and address are also
returned to the MCP and stored in MCP control register 2. The read/write bit is zero in the return
frame. Because the addressed register is updated at the end of subframe 0, the data returned during
the frame in which the write occurred represents the previous contents of the register. The updated
value is returned during the next data frame.
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Audio Data 0 0 0 0
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Telecom Data 0 0