FRS Signalling Processor
CMX882
0
1.6.13
Bit:
$CA and $CB TX DATA & XTCSS Codes: 2 x 16-bit write-only
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Tx MSK Data Byte 0
Tx MSK Data Byte 1
$CA
(Frame Head: Address byte)
Tx Data Byte 2*
(Frame Head: Size / Information byte)
Tx Data Byte 3*
$CB*
XTCSS Tone 3 (S1)
XTCSS Tone 2 (S0)
0
0
0
0
0
0
0
*Register $CB is only used for Type 4 and 5 data formats and Frame Heads, the Tx buffer is effectively 4 bytes long in these cases.
These 2 words hold next 2 bytes (Byte 0 and 1) or 4 bytes (Bytes 0, 1, 2 and 3) of MSK data to be
transmitted. Outgoing data is continuous, if new data is not provided before the current data has been
transmitted the current data will be re-transmitted, until new data is provided. Transmission of current
data will be completed before transmission of newly loaded data begins. See section 1.5.5.6.
$CB holds the codes to be used when transmitting an XTCSS type tone set. Each 4 bits define the In-
band tone used, see Table 6 In-band Tones. S0 and S1 are the information section of the 4 tone set.
This register must be set to the required value before XTCSS transmission is enabled. For more details
see section 1.5.6. Note The address used is defined in the Audio & Device Address Control register.
Although $CB holds both Tx data and Tx XTCSS tone information, these functions can not be used
simultaneously so no conflict will occur.
When transmitting formatted data packets the host must first load the correct Address and Size /
Information bytes for the following packet into register $CA. The CMX882 will automatically add the
Control byte (based on the settings in register $C7) and calculate the Frame Head Checksum A byte.
The CMX882 will read the Size and Message formatting information and automatically format all
following data; adding error correction bytes, adding pad bytes, interleaving, scrambling and calculating
and appending Checksum B as required. The only task the host need perform during the transmission of
a Frame is to download new data when it is required.
Note: These 2 words must be written separately. i.e. Two 16 bit C-BUS transactions.
1.6.14
$CD AUDIO TONE: 16-bit write only
Bit:
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
0
0
Audio Tone
When the required bits of the Mode Control register ($C1) are set an audio tone will be generated with
the frequency set by bits (11-0) of this register in accordance with the formula below. If bits 11-0 are
programmed with '0' no tone (i.e. Vbias) will be generated when the Audio Tone is enabled.
frequency = Audio Tone (i.e. 1Hz per LSB)
The Audio Tone frequency must only be set to generate frequencies from 300Hz to 3000Hz.
The host must suppress other voice band signalling and set the correct audio routing before generating
an audio tone and re-enable signalling and audio routing on completion of the audio tone. The timing of
intervals between these actions is also controlled by the host µC.
This register may be written to whilst the audio tone is being generated, any change in frequency will take
place after the end of the C-BUS write to this register. This allows complex sequences (e.g. ring or alert
tunes) to be generated for the local speaker (Tx or Rx via the AUDIO pin) or transmitted signal (Tx via
the MOD1/2 pins).
2004 CML Microsystems Plc
45
D/882/7
CMLMICRO [ CML MICROCIRCUITS ]
