User's Manual

9/29/2004 OV4F2
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User Manual BCM2035
04/23/03
Broadcom Corporation
Document 2035-UM100-R Boot ROM Power-Up Sequence Page 35
CRYSTAL PROGRAMMING
The BCM2035 supports several crystal frequency selection modes. Auto crystal frequency detection is
supported in the presence of an external LPO clock. List of supported crystal frequencies are shown in
Table 6.
Crystal frequency settings can also be read from the EEPROM or programmed using a mini driver.
There are six options for programming the crystal frequency.
1. All modes and UPRX pin is ASSERTED When the boot-rom starts if UPRX is ASSERTED a baud rate of
up to 57600bps can be negotiated (using the character 0x55) for the purpose of downloading an encoded-
crystal-frequency-programming or *non-volatile-memory-programming-mini-driver. Downloading over
UPRX is the same as is described in 4 below without the use of any flow control.
2. All modes and UPRX pin is ASSERTED and CTS is ASSERTED.
If the boot rom firmware senses CTS TRUE following sensing UPRX TRUE a baud rate of up to 1.5Mbps
(at certain crystal frequencies) can be negotiated (using the 0x55 character) for the purpose of
downloading a non-volatile-memory-programming mini-driver. Important:
BCM2035 will not transmit RTS
until the 0x55 character is sampled and measured.
Table 6: 4-bit PLL_SEL Field of CLK_CTL Byte
Binary Decimal Crystal Frequency (Mhz)
0000 0 19.2
0001 1 19.68
0010 2 19.8
0011 3 12
0100 4 13
0101 5 7.68
0110 6 14.4
0111 7 16.8
1000 8 26
1001 9 20
1010 10 Variable/Wildcard
1011 11 18
1100 12 19.44
1101 13 16.2
1110 14 38.4
1111 15 15.36
Note
Non-volatile-memory refers to external serial-EEPROM or FLASH memories.