Motorola Internal Use
11
A008 / A6188+ – Circuit Description
5)
The unit will then follow on as in the sequence below:
6)
13 MHz clock
.
On Power Up there are 2 different reference clocks produced.
Initially, as soon as power is applied to the MAGIC IC the
crystal, Y200
, supported
by the
CRYSTAL_BASE
(MAGIC
Pin E1
) will emit a 26MHz signal to the
MAGIC IC
, which will internally be divided by 2 to give our external 13MHz clock.
This is then fed out of the MAGIC on
Pin J6
(
CLK_OUT
) and distributed to
Whitecap
Pin H10
(
CLKIN
), then from Whitecap to GCAP II
Pin F5
as
GCAP_CLK
. At the same time the 13MHz
Varactor Diode CR248
is producing an
output. This output is controlled in the following way: The 26MHz from
Y230
is
divided down to 200 kHz and fed to a phase comparator within the MAGIC. The
13MHz from
CR230
is also divided down and fed in to the phase comparator, the
difference in phase produces an error voltage that is fed onto the cathode of the
Varactor CR230
. Which regulates the output to a stable 13MHz clock. Once the
software is running and the logic side of the board has successfully powered up, the
CLK_SELECT
signal from Whitecap
Pin 1
is fed to MAGIC
Pin G6
. This in turn
RESET
SPI_CE
R/W
VCLK
DSC_EN
V1
UPLINK
500
0
50
100
200
300
250
350
150
400
450
EPROM CE
SRAM VB&LB
GCAP
SPI_CE MAGIC
CLK SELECT
DOWNLINK
BFSR 1.7 after RESET, BCKLR at 1.6s
