MT8924
control byte. The data byte contains the number of
the channel to be disconnected. The second byte
contains the opcode (D0-D3). One frame pulse
must
pass
between
disconnection
and
reconnection of the same channel.
Instruction 4 : Overflow Status Monitoring
This function extracts overflow status information
on all existing conferences and transfers it to the
microprocessor data bus. This instruction consists
of two control bytes which are differentiated by the
C/D control signal. C/D set Low reads the status of
the first eight conferences, while C/D set High
reads the status of the remaining two conferences.
A conference is in overflow when the
corresponding status bit is high.
Instruction 5 : PCM Mode Select
This function is used to set the PCM format. The
control byte from the microprocessor consists of
one data byte. It contains the Extra Bit E (D6), the
Format Bits F1-F0 (D5, D4), and the opcode (D0-
D3). The E bit must be high when the PCM frame
contains an extra bit (i.e. 1.544 Mb/s). Normally E
is Low. Bits F1-F0 are used to select the PCM byte
format, according to Table 2. After RESET the
default values correspond to F1 at Low and F0 at
High if A-Law is selected, and F1 at High and F0 at
High if
µ-Law
is selected. All channels must be
disconnected when the PCM mode select
instruction is sent. They must remain disconnected
for at least two frame pulses after the instruction is
sent. It is recommended that this instruction be
used immediately following a system reset (see
RESET pin description).
Preliminary Information
Instruction 6 : Status Monitoring
This function is a read operation which consists of
a data byte, a control byte, and a status byte. It
extracts information for test and diagnostic
purposes and transfers it to the microprocessor
bus. The first byte contains the channel number,
while the second byte contains the opcode (D0-
D3). The third byte contains the status information
about the operating mode of the channel (D4-D7);
the attenuation level (D2-D3); and the noise
suppression level (D0-D1).
8-8
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