GC1115 Datasheet, PDF (39/80 Pages) Texas Instruments – Crest Factor Reduction Processor

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IO_CONTROL 0x8
Type: Read/Write Value at RESET: 0x0000
GC1115
SLWS144 – FEBRUARY 2005
The IO_CONTROL register controls various input and output port characteristics.
BITS
0
1
2
3
4
[6:5]
7
8
[15:9]
DESCRIPTION
Input port format
0 = 2's complement
1 = unsigned
Output port format
0 = 2's complement
1 = unsigned
Output Port A enable⁽¹⁾
0 = high-impedance
state
1 = enabled
Output Port B enable⁽¹⁾
0 = high-impedance
state
1 = enabled
Output “force zeros⁽²⁾
0 = normal
1 = "force zeros"
Output sample width⁽³⁾
00: 18 bits
01: 16 bits
10: 14 bits
11: 12 bits
Reserved
Non-Port Output Enable⁽⁴⁾ 0 = high-impedance
state
1 = driven
Reserved
(1) If Bit 2 AND Bit 3 are both zeros, OUT_CLK, OUT_IQ_SEL, SYNC_OUT, and INT will all be put into
a high-impedance state.
(2) When forcing zeros, the output port format (Bit 1) determines the values used to drive the output
ports. Two's complement drives the output ports with all zeros, while unsigned drives the output ports
with a “1” for the MSB and zeros for all other output bits.
(3) The output samples are always MSB-justified. Bits [6:5] simply determine the GC1115’s internal
convergent rounding point for the output samples.
(4) Bit 8 affects all output pins (OUT_CLK, OUT_IQ_SEL, SYNC_OUT, and INT) except Port A and Port
B pins, which are separately enabled using Bits 2 and 3.
IO_MODE
0x9
Type: Read/Write Value at RESET: 0x0000
The IO_CONTROL register controls various input and output port characteristics.
BITS
0
1
[3:2]
[15:4]
DESCRIPTION
Number of channels
0 = one channel
1 = two channels
Input port I/Q mux
0 = parallel
1 = muxed
Bits [3:2]: One-channel output port mode:
Bits 3:2
OUT_A
OUT_B
00
Reserved
Reserved
01 (complex)
I/Q muxed samples
(not used)
10 (complex)
I sample
Q sample
11 (real)
Samples 0, 2, 4, . . .
Samples 1, 3, 5, . . .
During two-channel operation, the interp-by-4 mode determines which samples are carried
on Ports A and B:
Interp-b-4 mode
OUT_A
OUT_B
Bypass
Channel 0, I/Q muxed
Channel 1, I/Q muxed
2x (complex)
Channel 0, I/Q muxed
Channel 1, I/Q muxed
2x (real)
Channel 0, real samples
Channel 1, real samples
4x (real)
Channel 0, real samples
Channel 1, real samples
Reserved
39