DS606 Datasheet, PDF (2/32 Pages) Xilinx, Inc – Multi-master operation

XPS IIC Bus Interface (v2.03a)
Functional Description
Figure Top x-ref 1
PLB
32 64 128
Soft Reset
PLB Slave
Interface
Module
Reg
Interface
Interrupt ^{IIC2INTC_Irpt}
Control
Interrupts
Dynamic
Master
TX
FIFO
Rx
FIFO
IIC
Control
C_GPO_WIDTH
Sda_T
Sda_O
Sda_I
Scl_T
Scl_O
Scl_I
GPO
Figure 1: XPS IIC Top Level Block Diagram
Figure 1 illustrates the top-level block diagram for the XPS IIC Bus Interface module. The PLB Slave Interface
Module provides the transaction interface to the PLB bus. A register interface block implements the address map
and connectivity for the firmware to control IIC data transfer operations.
The XPS IIC does not provide explicit electrical connectivity to the IIC bus. The module expects the design to
include bi-directional I/O buffers which implement open collector drivers for the SDA and SCL signals.
Consequently, the user must provide external pull up devices to properly hold the bus at the logic 1 state when the
connection to ground is removed.
The user must pay proper attention to the Philips specification when setting the values of these pull up devices
(typically resistors) to both meet the Philips specification, the FPGA maximum ratings and the ratings of any
devices on the bus itself.
Multi Master Operation
The controller only participates in multi master arbitration when the bus is initially free when the attempt is made.
After it issues the START other masters may participate in addressing and the XPS IIC will correctly relinquish the
bus if another master presents a lower address then it presents. However, if the bus is not free, as indicated by SDA
being low and SCL high (the START has occurred), when the request to acquire the bus is made then the XPS IIC
will wait until the next bus free opportunity to arbitrate.
Dynamic IIC Controller Logic
The dynamic controller logic provides an interface to the XPS IIC controller that is simple to use. The dynamic logic
supports master mode only and 7 bit addressing only.
DS606 June 22, 2011
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