CMX138 CML Microcircuits, CMX138 Datasheet - Page 51

• Manufacturer Part Number: CMX138
• Description: Audio Scrambler and Sub-Audio Signalling Processor
• Manufacturer: CML Microcircuits

Audio Scrambler and Sub-Audio Signalling Processor
9.2
In order to support radio systems that may not comply with the default settings of the CMX138, a set of
program register blocks is available to customise the features of the device. It is envisaged that these
blocks will only be written to following a power-on of the device and hence can only be accessed while the
device is in IDLE mode. Access to these blocks is via the Programming register ($C8).
All other interrupt sources should be disabled while loading the program register blocks.
The Programming register should only be written to when the Programming Flag bit (bit 0) of the Status
register is set to 1 and the Rx and Tx modes are disabled (bits 0 and 1 of the Mode Control register both
'0'). The Programming Flag is cleared when the Programming register is written to by the host. When the
corresponding programming action has been completed (normally within 250µs) the CMX138 will set the
flag back to 1 to indicate that it is now safe to write the next programming value. The Programming
register must not be written to while the Programming Flag bit is 0. Programming is performed by writing
a sequence of 16-bit words to the Programming register in the order shown in the following tables.
Writing data to the Programming register MUST be performed in the order shown for each of the blocks,
however the order in which the blocks are written is not critical. If later words in a block do not require
updating the user may stop programming that block when the last change has been performed. e.g: If
only 'Fine Output Gain 1' needs to be changed the host will need to write to P4.0, P4.1 and P4.2 only.
The user must not exceed the defined word counts for each block. P4.8 is allocated for production testing
and must not be accessed in normal operation.
The high order bits of each word define which block the word belongs to, and if it is the first word of that
block:
© 2008 CML Microsystems Plc
Programming Register Operation
Bit 15
X
X
X
X
X
1
0
Bit 14
X
X
1
1
1
1
0
Bit 13
X
X
0
0
1
1
Write to block 4 (14 bit words)
Bit 12
Page 51
X
X
0
1
0
1
1
2
Write to block 0 (12 bit words)
Write to block 1 (12 bit words)
Write to block 2 (12 bit words)
Write to block 3 (12 bit words)
st
nd
data for each block
and following data
Bit 11 – Bit 0
D/138_FI1.0/5
CMX138