
PSB 7230
Functional Blocks
Semiconductor Group
55
Data Sheet 1998-07-01
The interface to each of the audio channels is a 32-bit wide shift register. In receive
direction, when the shift register is filled to a programmable level (up to 32 bits), the
whole 32-bit shift register is loaded into the receive channel read register set accessible
from the DSP and from the host. Simultaneously, a maskable interrupt status is set.
Similarly, in the transmit direction, transmit channel data is loaded from the write register
pertaining to that channel (either from DSP or host register, as selected via a control bit)
into the transmit shift register when a selectable number of bits have been shifted out.
The buffering of up to 32 bits reduces the reaction time of the DSP software.
As an alternative to this, the audio channel data can also be loaded from the shift register
to the DSP/host registers (receive direction) and from the DSP/host registers into the
shift register (transmit direction) at the occurrence of the frame sync pulse. In this case
the number of significant bits in the registers is determined by the time-slot length
programmed on the receive/transmit line. The DSP/host has 125
μ
s to read/write the
register while new data is assembled or the contents of the shift register are transmitted,
during the following frame (this option could be used for DSP software synchronized on
the 8 kHz time base).
The audio channel registers, each of length 2 words/4 bytes, are (see
Section 3
):
The relevant parameters for controlling the transfer of the audio channels are
(independent for each channel):
The maskable interrupt status bits for controlling the transfer are:
or optionally:
RC1
XC1
Receive channel 1
Transmit channel 1
EN
LMOD
Enable channel
Load Mode (either once per frame, or after LBIT bits have been received/
transmitted)
Load Bits. Gives the number of bits (1 to 32) to be loaded, in multiples of
the physical time-slot length.
LBIT
BFUL
BEMP
Buffer full (RC1)
Buffer empty (XC1)
FSC
RFS
TFS
Frame Sync interrupt (FSC)
Frame Sync interrupt (RFS)
Frame Sync interrupt (TFS)