I
2
C-Master Core
Specification
Author: Richard Herveille
rherveille@opencores.org
Rev. 0.7
June 26, 2002
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Revision History
Rev. Date Author Description
0.1 17/02/01 Richard Herveille First draft release
0.2 01/03/01 Richard Herveille Some cleaning up throughout the document
Added ‘Programming Examples’ section
0.3 Richard Herveille Added some comments after core-changes
- added BUSY bit (status register)
- changed I2C IO for ASIC support
- added comment for FGPA IO
0.4 10/19/01 Richard Herveille Changed core’s databus size to 8bit.
Changed documentation to reflect changes.
Changed port names to new naming convention.
0.5 18/02/02 Richard Herveille Changed table headers.
Added OpenCores logo.
0.5a 05/02/02 Richard Herveille Reviewed entire document.
0.6 21/03/02 Richard Herveille Added Appendix A, Synthesis Results
0.7 25/06/02 Richard Herveille Changed Prescale Register formula
OpenCores I
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C-Master core 6/26/2002
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Introduction
I2C is a two-wire, bi-directional serial bus that provides a simple and efficient method of
data exchange between devices. It is most suitable for applications requiring occasional
communication over a short distance between many devices.
The interface defines 3 transmission speeds:
- normal: 100Kbps
- fast: 400Kbps
- high speed: 3.5Mbps
Only 100Kbps and 400Kbps modes are supported directly.
The I2C standard is a true multi-master bus including collision detection and arbitration
that prevents data corruption if two or more masters attempt to control the bus
simultaneously. This core, however, supports only single master operations, in which the
core is the master.
FEATURES
• Software programmable clock frequency
• Software programmable acknowledge bit
• Interrupt driven data-transfers
• Start/Stop/Repeated Start/Acknowledge generation
• Supports Clock Stretching/Wait state generation
• Single Master Operation
• Operates from a wide range of input clock frequencies
• Static synchronous design
• Fully synthesizable
OpenCores I
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C-Master core 6/26/2002
www.opencores.org Rev 0.7 Preliminary 2 of 15
2
IO ports
2.1 Core Parameters
Parameter Type Default Description
ARST_LVL Bit 1’b0 Asynchronous reset level
2.1.1 ARST_LVL
The asynchronous reset level can be set to either active high (1’b1) or active low (1’b0).
2.2 WISHBONE interface signals
Port Width Direction Description
wb_clk_i 1 Input Master clock
wb_rst_i 1 Input Synchronous reset, active high
arst_i 1 Input Asynchronous reset
wb_adr_i 3 Input Lower address bits
wb_dat_i 8 Input Data towards the core
wb_dat_o 8 Output Data from the core
wb_we_i 1 Input Write enable input
wb_stb_i 1 Input Strobe signal/Core select input
wb_cyc_i 1 Input Valid bus cycle input
wb_ack_o 1 Output Bus cycle acknowledge output
wb_inta_o 1 Output Interrupt signal output
arst_i is not a WISHBONE compatible signal. It is provided for FPGA implementations.
Using [arst_i] instead of [wb_rst_i] can result in lower cell-usage and higher
performance, because most FPGAs provide a dedicated asynchronous reset path. Use
either [arst_i] or [wb_rst_i].
