GT-64260A Design Guide
Doc. No. MV-S300165-00, Rev. A
CONFIDENTIAL
Copyright © 2002 Marvell
Page 72
Document Classification: Proprietary Information
May 21, 2002, Preliminary
Note
When he I
2
C Control register’s
I2CEn
bit [6] is set to ’0’, at offset 0xc008, the GT-64260A does not monitor
SDA and SCL. This effectively disables both the master and slave. Actually, the master can still transmit
(send address with R/W command) but it can't get the data returned or send an acknowledgement.
7.5.3 Serial ROM Initialization
If serial ROM initialization is enabled (AD[0] pin sampled high on SysRst* de-assertion), the GT-64260A I
2
C mas-
ter starts reading initialization data from the serial ROM and writes it to the appropriate registers.The serial ROM
initialization enables the user to initialize the GT-64260A internal registers, configuration registers, and other
devices connected on the PCI.
The serial ROM initialization must implement access to address 0x1400xxxx, since the I
2
C interface does not
sample the internal base setting at reset. This is not correct for the CPU interface, when the internal base is set to
0xf1000000, the CPU must access the GT-64260A internal registers at 0xf1 offset. It is possible to con-
figure to the internal base register through the serial ROM. In this case, all of the following accesses to the regis-
ters must correspond to this value. For example, if the Serial ROM includes the following lines:
0x14000068
0x00000f20
All the access following this line must be written to 0xF2000000. For example:
0xf2000000
0x4281a8ff
For more information on the serial ROM initialization, see the GT-64260A datasheet’s "Serial ROM Initialization"
section and the
3.5.1 "MPC745x Burst to Boot Address" on page 21
for an serial ROM initialization example.
Note
Make sure that all the reset configuration strapping required by the GT-64260A with serial ROM
initialization are pulled to the correct values (the same value configured in the serial initialization). For
more information, see the GT-64260A datasheet’s "Reset Configuration" section and the latest Datasheet
Changes and Update document.
7.6
Baud Rate Generator
The GT-64260A implements two Baud Rate Generators (BRG) that select one of the input clocks:
•
TClk – GT-64260A internal clock, the same clock as the SDRAM interface.
•
BclkIn – multiplexed on the MPP interface.
•
SClk[1:0] – MPSC port 0 or port1 serial clock.
•
TSClk[1:0] – MPSC port 0 or port1 transmit serial clock.
The BRGs use these source clocks to generate a derived clock, depending on the BRGx Configuration register’s
CDV
bits [15:0], at offsets 0xB200 or 0xB208. For more information, see the GT-64260A datasheet’s "Baud Rate
Generators" Section.