CMX838 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX838' PDF : 71 Pages View PDF
FRS/PMR446/GMRS Family Radio Processor
CMX838
5.1.2.17 SUBAUDIO STATUS Register ($94)
Bit(s)
SYNTH_IRQ
Bit 7
DECODER
STATUS
Bit 6
TONE INDEX
NUMBER
Bit 5-0
Description
This bit indicates whether the synthesizer lock detector issued an IRQ since the last
read of the synthesizer status register. Once the lock detector issues an IRQ this bit
becomes a logic ‘1’ and the chip IRQ pin is pulled low. SYNTH_IRQ bit remains a logic
‘1’ until the synthesizer status register is read. However, the chip’s IRQ is cleared as
soon as this subaudio status register is read. In other words, when servicing an IRQ,
read the subaudio status register and check this bit to determine if the synthesizer
needs servicing.
In RX mode, the decode status bit is a logic one when an enabled decoder senses that
the input signal matches its center frequency and is of sufficient quality to decode
In TX mode, bits 6-0 are normally zero, but take the decimal value 127 to indicate when
the TX timer has expired.
Reading the status register resets bits 6-0 to zero as well as clearing the IRQ in TX
mode to allow recurring indication of TX timer expiration. In RX mode, only the IRQ is
cleared on reading this status register, while the decode status and tone index are
maintained and continuously reported here.
Refer to Table 2 for supported Tone List and their index numbers.
Index numbers 1-51 indicate a matching decoder (enabled decoder index may be
reported before the full decode qualification of 2 matching measurements).
In TX mode, bits 6-0 are normally zero, but take the decimal value 127 to indicate when
the TX timer has expired.
If the input signal does not contain a subaudio signal that matches an enabled
decoder’s center frequency then the decoder status bit is a logic zero – in this case the
decoder index number is reported as:
• 62 if there is a significant subaudio frequency present outside the bandwidth of
any enabled decoder.
• 63 if the no tone timer has expired indicating (i.e. there is no significant
subaudio frequency present currently)
• 0 if no subaudio signal has been seen since the subaudio processor was
enabled or most recently placed in RX mode.
• Any enabled index, if the last frequency measurement indicates that enabled
tone may be present but has not yet been fully qualified.
Table 20: SUBAUDIO STATUS Register ($94)
5.1.2.18 8 BIT SUBAUDIO TASK DATA Register ($95)
Bit(s)
Description
Bit 7-0
This register is used to download 8 bit initialization/configuration data to the subaudio
processor. Refer to section 4.2.4 for task descriptions.
Table 21: 8 BIT SUBAUDIO TASK DATA Register ($95)
2003 CML Microsystems Plc
42
D/838/8
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