EF_I2C

I2C master controller with an APB interface

The wrapped IP

The IP comes with an APB Wrapper.

Wrapped IP System Integration

EF_I2C_APB INST (
        `TB_APB_SLAVE_CONN,
        .scl_i(scl_i),
        .scl_o(scl_o),
        .scl_oen_o(scl_oen_o),
        .sda_i(sda_i),
        .sda_o(sda_o),
        .sda_oen_o(sda_oen_o),
        .i2c_irq(i2c_irq)
);

NOTE: `TB_APB_SLAVE_CONN is a convenient macro provided by BusWrap.

Implementation example

The following table is the result for implementing the EF_I2C IP with different wrappers using Sky130 PDK and OpenLane2 flow.

Module	Number of cells	Max. freq
EF_I2C	TBD	TBD
EF_I2C_APB	TBD	TBD

The Programmer's Interface

Registers

Name	Offset	Reset Value	Access Mode	Description
Command	0004	0x00000000	w	bit 0-6: cmd_address, bit 8: cmd_start, bit 9: cmd_read, bit 10: cmd_write, bit 11: cmd_wr_m, bit 12: cmd_stop. Setting more than one command bit is allowed. Start or repeated start will be issued first, followed by read or write, followed by stop. Note that setting read and write at the same time is not allowed, this will result in the command being ignored.
Data	0008	0x00000000	w/r	bit 0-7: data, bit 8: data_valid, bit 9: data_last
PR	000c	0x00000000	w	prescale = Fclk / (FI2Cclk * 4)
IM	ff00	0x00000000	w	Interrupt Mask Register; write 1/0 to enable/disable interrupts; check the interrupt flags table for more details
RIS	ff08	0x00000000	w	Raw Interrupt Status; reflects the current interrupts status;check the interrupt flags table for more details
MIS	ff04	0x00000000	w	Masked Interrupt Status; On a read, this register gives the current masked status value of the corresponding interrupt. A write has no effect; check the interrupt flags table for more details
IC	ff0c	0x00000000	w	Interrupt Clear Register; On a write of 1, the corresponding interrupt (both raw interrupt and masked interrupt, if enabled) is cleared; check the interrupt flags table for more details

Command Register [Offset: 0x4, mode: w]

bit 0-6: cmd_address, bit 8: cmd_start, bit 9: cmd_read, bit 10: cmd_write, bit 11: cmd_wr_m, bit 12: cmd_stop. Setting more than one command bit is allowed. Start or repeated start will be issued first, followed by read or write, followed by stop. Note that setting read and write at the same time is not allowed, this will result in the command being ignored.

bit	field name	width	description
0	cmd_address	7	I2C address for command
8	cmd_start	1	set high to issue I2C start, write to push on command FIFO
9	cmd_read	1	set high to start read, write to push on command FIFO
10	cmd_write	1	set high to start write, write to push on command FIFO
11	cmd_write_multiple	1	set high to start block write, write to push on command FIFO
12	cmd_stop	1	set high to issue I2C stop, write to push on command FIFO

Data Register [Offset: 0x8, mode: w/r]

bit 0-7: data, bit 8: data_valid, bit 9: data_last

bit	field name	width	description
0	data	8	I2C data, write to push on write data FIFO, read to pull from read data FIFO
8	data_valid	1	indicates valid read data, must be accessed with atomic 16 bit reads and writes
9	data_last	1	indicate last byte of block write (write_multiple), must be accessed with atomic 16 bit reads and writes

PR Register [Offset: 0xc, mode: w]

prescale = Fclk / (FI2Cclk * 4)

Interrupt Flags

The wrapped IP provides four registers to deal with interrupts: IM, RIS, MIS and IC. These registers exist for all wrapper types generated by the BusWrap bus_wrap.py utility.

Each register has a group of bits for the interrupt sources/flags.

• IM: is used to enable/disable interrupt sources.

• RIS: has the current interrupt status (interrupt flags) whether they are enabled or disabled.

• MIS: is the result of masking (ANDing) RIS by IM.

• IC: is used to clear an interrupt flag.

The following are the bit definitions for the interrupt registers:

Bit	Flag	Width	Description
0	MISS_ACK	1	Slave ACK is missed
1	CMDE	1	Command FIFO is Empty
2	CMDF	1	Command FIFO is Full
3	CMDOVF	1	Command FIFO overflow; write 1 to clear
4	WRE	1	Write FIFO is Empty
5	WRF	1	Write FIFO is Full
6	WROVF	1	Write FIFO overflow; write 1 to clear
7	RDE	1	Read FIFO is Empty
8	RDF	1	Read FIFO is Full

The Interface

Module Parameters

Parameter	Description	Default Value
DEFAULT_PRESCALE	Default value for Prescale; prescale = Fclk / (FI2Cclk * 4)	1
FIXED_PRESCALE	Prescale value is fixed or could be dynamically configured	0
CMD_FIFO	Command AXI4 FIFO enable	1
CMD_FIFO_DEPTH	Command AXI4 FIFO depth	32
WRITE_FIFO	Write AXI4 FIFO enable	1
WRITE_FIFO_DEPTH	Write AXI4 FIFO depth	32
READ_FIFO	Read AXI4 FIFO enable	1
READ_FIFO_DEPTH	Read AXI4 FIFO depth	32

Ports

Port	Direction	Width	Description
scl_i	input	1	i2c scl (Serial Clock) input
scl_o	output	1	i2c scl (Serial Clock) output
scl_oen_o	output	1	i2c scl (Serial Clock) output enable
sda_i	input	1	i2c scl (Serial Data) input
sda_o	output	1	i2c scl (Serial Data) output
sda_oen_o	output	1	i2c scl (Serial Data) output enable
i2c_irq	output	1	i2c interrupt
wbs_adr_i	input	3	wishbone input address
wbs_dat_i	input	16	wishbone input data
wbs_dat_o	output	16	wishbone data out
wbs_we_i	input	1	wishbone write enable
wbs_sel_i	input	2	wishbone select
wbs_stb_i	input	1	wishbone chip select
wbs_ack_o	output	1	wishbone acknowledge
wbs_cyc_i	input	1	wishbone bus cycle
i2c_scl_i	input	1	i2c scl (Serial Clock) input
i2c_scl_o	output	1	i2c scl (Serial Clock) output
i2c_scl_t	output	1	i2c scl (Serial Clock) tristate
i2c_sda_i	input	1	i2c scl (Serial Data) input
i2c_sda_o	output	1	i2c scl (Serial Data) output
i2c_sda_t	output	1	i2c scl (Serial Data) tristate
flags	output	16	i2c flags

F/W Usage Guidelines:

1. Set the prescaler by writing to PR register where prescaler = clk_frq / (I2C_clk * 4)
2. Write a command in the command register according to whether you want to read or write as well as the slave address.
3. Write the data in the data register if you are writing to slave or read the same register if you are reading from the slave.

Installation:

You can either clone repo or use IPM which is an open-source IPs Package Manager

• To clone repo: git clone https://https://github.com/efabless/EF_I2C
• To download via IPM , follow installation guides here then run ipm install EF_I2C

Run cocotb UVM Testbench:

In IP directory run:

cd verify/uvm-python/

To run testbench for design with APB

To run all tests:

make run_all_tests BUS_TYPE=APB

To run a certain test:

make run_<test_name> BUS_TYPE=APB

To run all tests with a tag:

make run_all_tests TAG=<new_tag> BUS_TYPE=APB