GP2021 Datasheet, PDF (37/62 Pages) Mitel Networks Corporation – GPS 12 channel Correlator Advance Information

GP2021
To find the duty cycle of the MAG signal, channel 11 is used.
The In–phase accumulator CH11_I_PROMPT will add –3 for
each MAG sample at High and will add –1 for each MAG
sample at Low. If the duty cycle is correct (30%), the sum will
be: –1.6 * (Number of samples) plus an allowance for the
imbalance of sampling at the beginning and end of the
integration period. The duty cycle may be calculated as
follows:
N = Total No of samples in integration period.
N MAG3 = Total No of samples for which MAG was
High
N MAG1 = Total number of samples for which MAG was
Low
ACC11 = Total value in the CH11_I_PROMPT
accumulator, as read after a DUMP.
N = N MAG3 + N MAG1 ,
ACC11 = –3 * N MAG3 –N MAG1
MAG duty cycle, Rm = Nmag3 / N = – (N + ACC11) / 2N
(nominally 0·30).
TM_TEST: When High this bit puts all the Tracking Modules
into a test mode, where it is possible to write to all
CHx_CARRIER_CYCLE_COUNTERs and all
CHx_CODE_PHASE_COUNTERs.
TEST_SOURCE: When High this bit enables a self–test
generator formed from the CH0 Code Generator. The data
replaces the SIGN0 and MAG0 inputs. It has a chip rate and
phase set by the CH0_CODE_DCO and a carrier frequency
set by the CH0_CARRIER_DCO. The code is set by writing
the appropriate start value into the CH0_SATCNTL register,
and the CH0_SLEW_COUNTER can be programmed to
delay the start of the code generation by a number of half code
chips. The three most significant bits of the Carrier DCO are
decoded to give the SIGN with 50% of Highs and the MAG with
25% of Highs. The sign of the data pattern is set by
TEST_DATA, EXORed with the CH0 C/A code.
TEST_DATA: This bit sets the sign of the modulation of
the test data generated when TEST_SOURCE is set.
TEST_CACODES: When High, the inverted PROMPT
codes for all channels, 0 to 11, are available for output on data
bus bits 0 to 11 and can be seen in parallel by a read to any
CH6 to CH11 read address.
EN_SCANPATH: When High the chip is in scan test
mode, whereby:
DISCIP 1
DISCOP
MULTI_FN_IO
NOPC/NINTELMOT
becomes
becomes
becomes
becomes
SCAN_IN
SCAN_OUT
SCANCLK
SCANSEL
It should be noted that the DISCOP = SCAN_OUT
function may be over–ridden by the
DISCOP_SELECT_100KHZ function of SYSTEM_SETUP. It
should also be noted that for correct operation the
MULTI_FN_IO pin should be configured as a Discrete or Scan
Clock Input via the IO_CONFIG register.
PATH_SEL<2:0>: To allow for simple factory testing of
the chip, the GP2021 contains six separate scan paths, one
for each of the major counters in the chip. Only one of these
paths may be enabled at any time and the scan path to be used
is selected via the PATH_SEL<2:0> bits as follows:
PATH_SEL<2:0>
000
001
010
011
100
101
11X
Scan Path Selected
RTC Counters
ACCUM_INT Counter
TIC Counter
100KHz Output Counter
Timemark Pulse Width
Counter
PLL_LOCK Filter
Counter
Not Used
TIMEMARK_CONTROL
(Write Address)
Bit
Bit name
15 to 7 not used
6 to 2 FREE_RUN_RATIO
1 FREE_RUN_TIMEMARK
0 ARM_TIMEMARK
The TIMEMARK Generator operates in one of two ways,
either in armed mode, (not related to ARM System Mode) or
in free run mode. In armed mode setting the
ARM_TIMEMARK bit arms the TIMEMARK generator which
subsequently produces a TIMEMARK output pulse coincident
with the next rising edge of TIC. This then resets the
ARM_TIMEMARK bit ready for a new arming sequence in the
future. Alternatively, the TIMEMARK generator can be used in
free–run mode, by setting the FREE_RUN_TIMEMARK bit
High. This disables the ARM_TIMEMARK bit. In free run mode
a TIMEMARK pulse is produced coincident with the first rising
edge of TIC after the FREE_RUN_TIMEMARK bit has been
set, and then on an integer number of TIC’s determined by the
FREE_RUN_RATIO bits. In free run mode the TIMEMARK
period is:
TIMEMARK Period = (FREE_RUN_RATIO + 1) * TIC Period
(Free run mode)
All the bits of TIMEMARK_CONTROL are cleared to Low
by a Master Reset.
X_DCO_INCR_HIGH
(Write Address)
This register may be used to write the high bits for any
Carrier or Code DCO in any channel. A write to
X_DCO_INCR_HIGH must always be followed by a write to
the appropriate CHx_CARRIER_DCO_INCR_LOW or
CHx_CODE_DCO_INCR_LOW to define the destination and
to complete the action.
Using X_DCO_INCR_HIGH rather than CHx_CARRIER
–_DCO_INCR_HIGH gives a quicker way of loading the whole
DCO’s values because the _LOW write may follow the
X_DCO_INCR HIGH write immediately (without incurring a
300ns wait).
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