
1996 Oct 29
95
Philips Semiconductors
Objective specification
GSM signal processing IC
PCF5083
9.4.4.2
Loop-back mode
During TCH_LOOP mode the CP_TX_SPEECH and
CP_RX_SPEECH procedures have to be replaced by the
following procedures:
Replacement for CP_tx_speech:
MP_read_audio_in_fifo (SCRATCH_BUFF, 160)
DB_copy_buffer (TCH_LOOP_BUFF,
SCRATCH_BUFF, 0, 0, 82)
CM_convert_tchfs_data(bfi_sig_flag)
CM_encoder_tchfs(dtx_flag, taf, facch_flag,
facch_msg[12])
CP_tx_four_normal_bursts (tsc)
Replacement for CP_rx_speech:
CM_decoder_tchfs( )
DB_copy_buffer(SCRATCH_BUFF,
TCH_LOOP_BUFF, 0, 0, 82)
DB_fill_buffer(SCRATCH_BUFF, 0, 0, 160)
MP_write_audio_out_fifo(SCRATCH_BUFF, 160).
9.4.4.3
Initialization messages for normal mode
Before the first TDMA frame of a TCH/FS can be
processed, several initialization messages have to be sent
to the DSP. Initialization is done in 2 DMA frames as
shown in Table 72.
The first one or two results of CM_decoder_TCH are
based on only partially observed input data, since
8 successive normal bursts are needed due to
interleaving.
Table 71
Parameter nb
nb
t2
s
13
14
15
16
4
3
2
5
6
0
1
2
3
11
4
5
6
7
8
9
12
17
18
19
20
21
22
23
24
25
10
Table 72
Initialization messages
Table 73
Initialization procedures
Notes
1.
2.
Procedures to be started via EXEC_PROC in TDMA frame FN (TCH/FS normal mode).
t1
s
= FN
s
divided by 26
×
51;
t2
s
= FN
s
modulo 26;
t3
s
= FN
s
modulo 51.
The parameter nb determines the number of normal bursts to be written into the modulator output FIFO in the
initialization frame. It depends on the frame number of the 1st processed frame in accordance with Table 71.
3.
TDMA
FRAME
FN
s
2
EXPLANATION
In this TDMA frame the message for initialization of speech CODEC, channel CODEC and ciphering are
sent to the DSP. Furthermore the modulator out FIFO is filled with the proper number of bursts and
synchronization between TDMA frame timing and speech frame timing is performed and the audio
interface is enabled by setting the IO1 pin. No data is received or transmitted within this frame.
In this TDMA frame the EXEC_PROC messages for the procedures processing the data of frame FN
s
are sent to the DSP. No data is received or transmitted within this frame.
In this TDMA frame the normal processing of receive and transmit data takes place.
FN
s
1
FN
s
fn
PROCEDURES
(1)
N
W
21
RX
TX
MX
FN
s
2
CP_start_TCHFS (enc_flag, dec_flag, t1
s
, t2
s
, t3
s
, kc[4], nb); notes 2 and 3
DB_write_register (11, 0x0100, 1); set IO1 = 1
The correct value for N
W
must be looked-up in Table 70
The correct value for N
W
must be looked up in Table 70
0
0
0
FN
s
1
FN
s
‘...’
‘...’
0
0
0
149
164
151