Baseband Processor For Mixed Mode Land Mobile Radio
CMX880
The xtal clock circuit is powered down by setting bit 3 to 1. On reset, bit 3 is cleared to 0, which enables the xtal
clock circuit. The CLOCK/XTAL pin can be driven by an external clock source, whether the clock circuit is
powered-up or powered-down.
If ‘EN RSSI Monitor’ bit 1 is set to 1, RSSI monitoring is enabled. The RSSI monitor will generate interrupts in
accordance with the settings of the interrupt mask bits. If ‘EN RSSI Monitor’ bit is cleared to 0, RSSI monitoring
is disabled and the auxilliary ADC is powered down.
If ‘RSSI Auto start-up’ bit 0 is set to 1, when the RSSI input rises above the ‘RSSI High Threshold’, the CMX880
will automatically start up the receiver and initiate received signal type identification. If ‘RSSI Auto start-up’ is
cleared to 0 the CMX880 will not automatically start-up, so it is up to the user to respond accordingly to RSSI
interrupts.
$C7 FFSK/MSK RX SYND: 16-bit write-only
$CA FFSK/MSK RX SYNC/SYNT: 16-bit write-only
Bit:
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SYND Pattern
SYNC/SYNT Pattern
The SYNC, SYNT and SYND define three programmable 16-bit synchronisation words that can be compared
with incoming RX data. The SYNT bit pattern is the inverse of the SYNC bit pattern which is programmed into
the ‘FFSK/MSK SYNC/SYNT’ register. The SYND pattern is programmed into the ‘FFSK/MSK SYND’ register.
When a match is found with an enabled sync pattern the signal is identified as an FFSK/MSK signal and the start
of an FFSK/MSK data transfer is indicated. Both these registers are set to correspond to the MPT1327 sync
pattern following a reset. The most significant bit (bit 15) of the sync pattern is received first.
$CB TX SELCALL TONE: 16-bit write only
Bit:
15
0
14
0
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Notone
Selcall Frequency Code
The ‘Selcall Tone Frequency’ bits define the tone in accordance with the formula below. If the tone frequency is
programmed with 0, or if the ‘Notone’ bit (bit 13) is set to 1, no Selcall tone will be transmitted.
When the ‘Notone’ bit is set to 0 and Selcall transmit mode is enabled, the Selcall tone is transmitted along with
the signal source defined by the ‘ANALOGUE OUTPUT PATH CONFIGURATION’ register and ‘TX MODE’
register settings.
The frequency of the transmitted Selcall tone is define according to the formula:
Frequency Code = (integer)(2.730625 ´ frequency)
It is up to the user/host mC to suppress voice data before initiating a Selcall tone transmit and to re-enable voice
data on completion of the Selcall tone transmit. Timing of the intervals between voice suppression, Selcall
transmit and re-enable voice is also controlled by the user/host mC.
ã 2001 Consumer Microcircuits Limited
46
D/880/1
CMLMICRO [ CML MICROCIRCUITS ]
