Motorola Internal Use
5
P7389i – Circuit Description
H3
. When the headset is connected an interrupt will be sent from
Headset Jack J504,
connection 1
as
HEAD_INT_L
to
Whitecap U800
Pin N3.
3)
Within the GCAP II the analogue audio will be converted to digital and clocked out
onto the
DIG_AUD
SPI bus to the
Whitecap U800
.
4)
It is within the Whitecap that all information about the transmission burst is
formulated i.e. The timing of the burst, the channel to transmit on, the error correction
protocol and in which frame the information will be carried to the base station. In
addition security and error correction / detection coding will be incorporated.
5)
All this information is then added to the digitised audio and is transferred to the
MAGIC DM DM U200
along a TX SPI bus. The bus is made up of
BCLKX
(Base
band Clock Transmit)
Pin B3
and
BDX
(Base band Data Transmit)
Pin B6
. The
timing for this data is already decided for the transmission burst, and therefore a
frame synch is not required.
6)
The SPI comes into the MAGIC DM at
Pin G7
(
BCLKX
) and
Pin J2
(
BDX
)
7)
The operation of the MAGIC DM is very complex and with respect to the transmit
path, integrates the functions of the Modem and its function of performing GMSK
(Gaussian Minimum Shift Keying) and also the functions of the TIC (Translational
Integrated Circuit).
8)
A very basic block view of how the transmit path works within the MAGIC DM is
demonstrated in: Fig 8.1
Internal MAGIC DM Operation
Fig 8.1
TX_CP
CLK
BDX
Look
Up
ROM
Σ
AFC
Channel
Info
Digital
representation
of TX VCO
F/B
Digital
representation
of RX VCO
CLK
MAGIC DM
now
compares previous
5 bits of previous
data instead of 4.