GP2021 Datasheet, PDF (27/62 Pages) Mitel Networks Corporation – GPS 12 channel Correlator Advance Information

GP2021
Tracking Channel Registers
ADDRESS (Hex)
ARM MODE
STANDARD
SYSTEM
INTERFACE
MODE
CNTL + 00
CNTL + 0
+ 04
+1
+ 08
+2
+ 0C
+3
+ 10
+4
+ 14
+5
+ 18
+6
+ 1C
ACCUM + 00
+7
ACCUM + 0
+ 04
+1
+ 08
+2
+ 0C
+3
WRITE FUNCTION
READ FUNCTION
SATCNTL
CODE PHASE COUNTER*
CARRIER_CYCLE_COUNTER*
CARRIER_DCO_INCR_HIGH
CARRIER_DCO_INCR_LOW
CODE_DCO_INCR_HIGH
CODE_DCO_INCR_LOW
EPOCH_COUNT_LOAD
CODE_SLEW_COUNTER
ACCUM_RESET
not used
CODE_DCO_PRESET_PHASE
CODE_SLEW
CODE_PHASE
CARRIER_CYCLE_LOW
CARRIER_DCO_PHASE
EPOCH (Latched0
CODE_DCO_PHASE
CARRIER_CYCLE_HIGH
EPOCH_CHECK (Not latched)
I_TRACK
Q_TRACK
I_PROMPT
Q_PROMPT
NOTE: The registers labelled * (the CODE_PHASE_COUNTER and CARRIER_CYCLE_CONTROL) can only be written
to if ‘Test’ mode has been selected by setting bit 3 of the TEST CONTROL register to High.
ADDRESS (Hex)
ARM SYSTEM
STANDARD
MODE
INTERFACE
MODE
200
80
204
81
208
82
20C
83
WRITE FUNCTION
STATUS
not used
not used
not used
READ FUNCTION
ACCUM_STATUS_C
MEAS_STATUS_A
ACCUM_STATUS_A
ACCUM_STATUS_B
In both the ACCUM and CNTL sections there are some
addresses labelled ALL or MULTI in place of CHx. Writing to
these addresses will write to all channels or to a selection set
by MULTI_CHANNEL_SELECT in one operation and so may
be used to initialise the system quickly or to load the next
search settings with little bus use. This is a write only function
and the corresponding CHx read functions are not available
at addresses labelled ALL or MULTI.
It can be seen that the addresses in CNTL are used to
control the device in write mode but give the Measurement
Data when in read mode.
Apart from the Code and Carrier DCO increment values
all data transfers are only 16 bit wide. Writes to the Code and
Carrier DCO’s are 32 bit data transfers where the _HIGH word
should be written first and will be retained in the 16 to 32 bit
interface until the _LOW word is written, which must occur as
the next write to the chip. All 32 bits will then be transferred into
the DCO increment register. Data is written to an input buffer
in the 16 to 32 bit interface and will be transferred to its
destination register during the next full cycle of the 7 (or 6)
phase clock. Write cycles should therefore have a period of at
least 300 ns. The X_DCO_INCR_HIGH may be used to write
the high bits of the increment number to any or all DCO’s as
an alternative to using the CHx_CODE
CARRIER_DCO_INCR– _HIGH addresses. By using this
address, there is no need to wait 300ns before writing the
_LOW part. For further information refer to General Interface
Timing in Microprocessor Interface section.
The bit assignments for the Correlator registers are given
below, but two write–only registers do not have any data bits,
these are:
(1) A write to the CHx_ACCUM_RESET register (irrespective
of what data is written) will reset the ACCUM_STATUS_A,
ACCUM_STATUS_B, and ACCUM_STATUS_C registers for
that channel.
(2) A write to the STATUS register (irrespective of what data
is written) will latch the state of the various status flags into
ACCUM_STATUS_A,
ACCUM_STATUS_B,
ACCUM_STATUS_C
Registers for all channels. This allows a polling based rather
than Interrupt driven tracking scheme.
The registers are listed in alphabetical order and not in
address order to allow easy reference to each section. Unless
otherwise stated the LSB is bit 0 and the MSB is bit 15 or as
far up the register as there is data. Note that most registers do
not have both read and write functions, and many addresses
are shared between read–only and write–only registers
having different functions.
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