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mode 00, write from master to slave works

This commit is contained in:
Peter McGoron 2022-07-21 01:09:45 -04:00
parent 6f000b64ec
commit c4f401cff2
3 changed files with 35 additions and 15 deletions
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2
Makefile
View File

@ -9,7 +9,7 @@ all: obj_dir/V${TESTBENCH_BASE}
./obj_dir/V${TESTBENCH_BASE} && gtkwave ${WAVEFILE}
obj_dir/V${TESTBENCH_BASE}.mk: ${FILES}
verilator --trace --cc --exe ${FILES} --top ${TESTBENCH_BASE}
verilator -Wall -Wno-unused -Wpedantic --trace --cc --exe ${FILES} --top ${TESTBENCH_BASE}
obj_dir/V${TESTBENCH_BASE}: obj_dir/V${TESTBENCH_BASE}.mk
make -C obj_dir -f V${TESTBENCH_BASE}.mk

24
spi_master.v
View File

@ -72,8 +72,22 @@ always @ (posedge clk) begin
idle_state();
finished <= 0;
end else begin
state <= ON_CYCLE;
/* at Mode 00, the transmission starts with
* a rising edge, and at mode 11, it starts
* with a falling edge. For both modes,
* these are READs.
*
* For mode 01 and mode 10, the first
* action is a WRITE.
*/
if (POLARITY == PHASE) begin
mosi <= to_slave[WID-1];
send_buf <= to_slave << 1;
state <= CYCLE_WAIT;
end else begin
send_buf <= to_slave;
state <= ON_CYCLE;
end
end
end
ON_CYCLE: begin
@ -84,7 +98,7 @@ always @ (posedge clk) begin
read_data();
end
if (POLARITY == 1) begin
if (POLARITY == 0) begin
bit_counter <= bit_counter + 1;
end
end else begin // falling edge
@ -94,7 +108,7 @@ always @ (posedge clk) begin
write_data();
end
if (POLARITY == 0) begin
if (POLARITY == 1) begin
bit_counter <= bit_counter + 1;
end
end
@ -103,7 +117,9 @@ always @ (posedge clk) begin
CYCLE_WAIT: begin
if (timer == CYCLE_HALF_WAIT) begin
timer <= 0;
if (bit_counter == WID) begin
// Stop transfer when the clock returns
// to its original polarity.
if (bit_counter == WID && sck == POLARITY) begin
state <= WAIT_FINISHED;
end else begin
state <= ON_CYCLE;

16
spi_slave.v
View File

@ -55,11 +55,7 @@ always @ (posedge clk) begin
err <= 0;
end
2'b10: begin // falling edge
if (bit_counter == WID) begin
finished <= 1;
end else begin
err <= 1;
end
end
2'b11: begin
case ({sck_delay, sck})
@ -70,10 +66,14 @@ always @ (posedge clk) begin
read_data();
end
if (POLARITY == 1) begin
if (POLARITY == 0) begin
if (bit_counter == WID) begin
err <= 1;
end else begin
bit_counter <= bit_counter + 1;
end
end
end
2'b10: begin // falling edge
if (PHASE == 1) begin
read_data();
@ -81,10 +81,14 @@ always @ (posedge clk) begin
write_data();
end
if (POLARITY == 0) begin
if (POLARITY == 1) begin
if (bit_counter == WID) begin
err <= 1;
end else begin
bit_counter <= bit_counter + 1;
end
end
end
default: ;
endcase
end