CMX983 Datasheet, PDF (35/93 Pages) CML Microcircuits – Programmable Channel Filter

Analogue Front End (AFE) for Digital Radio
CMX983
RX_ADDR - $2D: 8-bit Write
Reset value = $00
Bit:
7
6
5
4
3
2
1
0
0
Rx coefficient address pointer
The Rx coefficient address pointer determines the address at which data gets written during a C-BUS
write to any of the four Rx coefficient RAMs. The Rx coefficient address pointer automatically
increments after each 16-bit coefficient value is written, so if the coefficients are written in an
ascending sequence the pointer only needs to be initialised once before each bank of coefficients is
loaded.
RX_STATUS - $2E: 16-bit Read
Reset value = $0101
Bit:
15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
0
Ch. B
vern.
error
Ch. B
FIR
error
Ch. B
2^nd bit
select
over-
flow
Ch. B
1^st bit
select
over-
flow
Ch. B
input
over-
flow
Ch. B
buffer
over-
run
Ch. B
idle
0
Ch. A
vern.
error
Ch. A
FIR
error
Ch. A
2^nd bit
select
over-
flow
Ch. A
1^st bit
select
over-
flow
Ch. A
input
over-
flow
Ch. A
buffer
over-
run
Ch. A
idle
RX_STATUS b15: Reserved, set to 0
RX_STATUS b14: Channel B vernier error
This bit gets set if Rx channel B is enabled and the vernier value is incorrect, i.e. it has been set to a
value equal to or greater than first downsample rate in channel B. To clear this bit, first correct the
error (or disable the channel) then read the RX_STATUS register again.
RX_STATUS b13: Channel B FIR error
This bit gets set, if Rx channel B is enabled, if a new output value from the FIR filter is not ready when
the rising edge of the CR3 clock occurs. This happens if the FIR filter length is too large for the
chosen clock and sample rates. When this happens, data sent from the FIR filter to the Rx serial port
may become lost or corrupted. This bit gets cleared only when RX_STATUS is read.
RX_STATUS b12: Channel B 2^nd bit selector overflow
This bit gets set to 1 when the channel B 2^nd bit selector output value saturates to maximum positive
($7FFF) or maximum negative ($8000). This bit gets cleared only when RX_STATUS is read.
RX_STATUS b11: Channel B 1^st bit selector overflow
This bit gets set to 1 when the channel B 1^st bit selector output value saturates to maximum positive
($7FFFF) or maximum negative ($80000). This bit gets cleared only when RX_STATUS is read.
RX_STATUS b10: Channel B input overflow
This bit gets set to 1 when the channel B input exceeds a pre-programmed limit (see section 9.1).
This bit gets cleared only when RX_STATUS is read.
RX_STATUS b9: Channel B buffer overrun
This bit gets set to 1 whenever Rx channel B generates a data sample before the Rx serial port is
able to take it, for instance if the Rx serial port gets disabled or is configured to run too slowly. When
 2015 CML Microsystems Plc
35
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