Cal Poly CARP SOC

• Architecture Overview
• OBI Bus And Peripherals
  • Memory Map
    • Boot ROM and Boot Configs
    • XIP QSPI Flash Controller (QSPI_1)
    • Monitor Interrupt Generator
  • Wishbone-OBI Bridge
  • OBI Bus Protocol
• IO Assignment
  • GPIO Pins
  • Logic Analyzer Pins
    • Logic Analyzer Sample Channels
  • Pin Descriptions (QFN64 9x9 0.5)

Architecture Overview

The CARP SOC is composed of 2 RISC-V RV32I processors, a primary processor (the "CARP Core") and a processor that manages and monitors the CARP Core (the "Monitor Core"). The processors each have their own address space, volatile and (off-chip) non-volatile memory, clocks, resets, and peripherals. The Monitor Core and its peripherals have their documentation here, while the CARP Core and its peripherals are documented below.

OBI Bus And Peripherals

Memory Map

The main memory interconnect used on the SoC is a subset of OpenHW Group's Open Bus Interface (OBI). The subset we are using is the same subset used by OpenHW Groups's RI5CY Core, and its behavior is fully described in the OBI-1 specification.

Start Address	End Address	Section
0x0000_0000	0x0000_0FFF	Bootloader
0x0000_1000	0x0FFF_FFFF	--
0x1000_0000	0x1000_1FFF	Peripheral Register File
0x1000_1000	0x1FFF_FFFF	--
0x2000_0000	0x3FFF_FFFF	512Mb Flash
0x4000_0000	0x7FFF_FFFF	--
0x8000_0000	0x8000_4FFF	20 kB SRAM
0x8000_5000	0xEFFF_FFFF	--
0xF000_0000	0xF000_0003	Monitor Interrupt Generator
0xF000_0004	0xFFFF_FFFF	--

Boot ROM and Boot Configs

On boot, the core resets the program counter to an address based on the boot_sel input.

boot_sel	copy_boot_sel	Program Counter Reset Address	Function
0	0	0x0000_0000	Copies 512 words from QSPI (starting from 0x2000_0000 into SRAM), then jumps to SRAM at 0x8000_0000.
0	1	0x0000_0000	Jumps to QSPI at 0x2000_0000 and begins executing in place.
1	x	0x8000_0000	Starts execution from the internal SRAM. This assumes that the caravel has loaded a program into the SRAM prior to startup.

XIP QSPI Flash Controller (QSPI_1)

The QSPI controller at 0x2000_0000 can support up to 512MB external QSPI memory. This flash can be programmed via the housekeeping SPI (SPI_0) in pass-thru mode. There is a 32 bit control register located at address 0x3FFF_FFFF, described below.

Bit(s)	Description
31	MEMIO Enable (reset=1, set to 0 to bit bang SPI commands)
30:23	Reserved (read 0)
22	DDR Enable bit (reset=0)
21	QSPI Enable bit (reset=0)
20	CRM Enable bit (reset=0)
19:16	Read latency (dummy) cycles (reset=8)
15:12	Reserved (read 0)
11:8	IO Output enable bits in bit bang mode
7:6	Reserved (read 0)
5	Chip select (CS) line in bit bang mode
4	Serial clock line in bit bang mode
3:0	IO data bits in bit bang mode

The following settings for CRM/DDR/QSPI modes are valid:

CRM	QSPI	DDR	Read Command Byte	Mode Byte
0	0	0	03h Read	N/A
0	0	1	BBh Dual I/O Read	0xFF
1	0	1	BBh Dual I/O Read	0xA5
0	1	0	EBh Quad I/O Read	0xFF
1	1	0	EBh Quad I/O Read	0xA5
0	1	1	EDh DDR Quad I/O Read	0xFF
1	1	1	EDh DDR Quad I/O Read	0xA5

Monitor Interrupt Generator

There is a 3 bit interrupt vector for the Monitor Core that can be generated by the CARP SOC by writing to address 0xF000_0000. The two least significant bits are generated by the two least significant bits of the write data, and the third bit of the interrupt vector is reserved for hardware-generated interrupts

irq[2]	irq[1]	irq[0]
Hardware Error	Write Data bit 1	Write Data bit 0

Wishbone-OBI Bridge

The wishbone port on the SOC allows the Monitor Core to read and write to the CARP Core's SRAM, as long as the wishbone enable control is set (see Logic Analyzer). The SRAM is located at address 0x3000_0000 in the wishbone address space. The Wishbone-OBI bridge handles clock domain crossing, protocol conversion, and address translation.

OBI Bus Protocol

The specific signals are enumerated below:

Pin Name	Pin Count	Direction	Description
req	1	Controller -> Memory	Asserted by the controller to request a memory transaction. The controller is responsible to keep all address signals valid while req is high.
gnt	1	Memory -> Controller	Asserted by the memory system when new transactions can be accepted. A transaction is accepted on the rising edge of the clock if req and gnt are both high.
addr	32	Controller -> Memory	Address output from the controller to access memory location
we	1	Controller -> Memory	Asserted by the controller to indicate a write operation
be	4	Controller -> Memory	Byte enable output (strobe), to specify which bytes should be accessed
wdata	32	Controller -> Memory	Write data output from the controller to be written to memory
rvalid	1	Memory -> Controller	Asserted by the memory system to signal valid read data. The read response is completed on the first rising clock edge when rvalid is asserted. rdata must be valid as long as rvalid is high.
rdata	32	Memory -> Controller	Read data input to the controller from the memory system

IO Assignment

GPIO Pins

There are 38 user-programmable IO pins:

Pin #	Input Pin	Output Pin	Output Enable	Description
0	JTAG	x	x	reserved
1	x	SPI_0_SDO	1	SPI 0 (Housekeeping SPI)
2	SPI_0_SDI	x	0	SPI 0 (Housekeeping SPI)
3	SPI_0_CSB	x	0	SPI 0 (Housekeeping SPI)
4	SPI_0_SCK	x	0	SPI 0 (Housekeeping SPI)
5	copy_boot_sel	x	x	1 = copy 512 words from flash to SRAM and jump to SRAM. 0 = jump to flash.
6	boot_sel	x	x	Hard select for the bootloader. (see Boot ROMs)
7	rst_hard_n	x	x	Hard reset input, such as for a reset button (active low)
8	x	o_qspi_cs_n	0	QSPI chip select (active low)
9	x	o_qspi_sck	0	QSPI clock
10	i_qspi_dat[0]	o_qspi_dat[0]	Determined by o_qspi_mod	QSPI data bit 0
11	i_qspi_dat[1]	o_qspi_dat[1]	Determined by o_qspi_mod	QSPI data bit 1
12	i_qspi_dat[2]	o_qspi_dat[2]	Determined by o_qspi_mod	QSPI data bit 2
13	i_qspi_dat[3]	o_qspi_dat[3]	Determined by o_qspi_mod	QSPI data bit 3
14				(Peripherals)
15				(Peripherals)
16				(Peripherals)
17				(Peripherals)
18				(Peripherals)
19				(Peripherals)
20				(Peripherals)
21				(Peripherals)
22				(Peripherals)
23				(Peripherals)
24				(Peripherals)
25				(Peripherals)
26				(Peripherals)
27				(Peripherals)
28				(Peripherals)
29				(Peripherals)
30				(Peripherals)
31				(Peripherals)
32				(Peripherals)
33				(Peripherals)
34				(Peripherals)
35				(Peripherals)
36				(Peripherals)
37				(Peripherals)

Logic Analyzer Pins

There are 128 logic analyzer io pins controllable from the caravel.

Pin #'s	Signal Name	Description
3:0	reset_soft_n	As long as the value 0xA is written to this nibble, the user area will reset
7:4	wishbone_enable	As long as the value 0xA is written to this nibble, the data port of the onboard RAM will be given to the wishbone bus. The CARP core will not have access to the RAM.
11:8	halt_clock	As long as a 0xA is written to this nibble, the clock will be held in its current position (high or low).
14:12	la_mux	Logic Analyzer sample channel MUX select. The channels (see "Sample Channels" below) can be selected between using these bits.
15	clk_masked	System On Chip Clock
127:16	Sample Channels	112 Bit digital sample channels. These can be selected between using la_mux.

Logic Analyzer Sample Channels

Pin #	CH 0	CH 1	CH 2	CH 3	CH 4	CH 5	CH 6	CH 7
16	dmem_addr[0]	imem_addr[0]	sram_d_muxed_addr[0]	sram_i_addr[0]	peripheral_addr[0]	rf_port1_reg[0]	gpio_i[5]	p_interrupts[0]
17	dmem_addr[1]	imem_addr[1]	sram_d_muxed_addr[1]	sram_i_addr[1]	peripheral_addr[1]	rf_port1_reg[1]	gpio_i[6]	p_interrupts[1]
18	dmem_addr[2]	imem_addr[2]	sram_d_muxed_addr[2]	sram_i_addr[2]	peripheral_addr[2]	rf_port1_reg[2]	gpio_i[7]	p_interrupts[2]
...	...	...	...	...	...	...	...	...
20	dmem_addr[4]	imem_addr[4]	sram_d_muxed_addr[4]	sram_i_addr[4]	peripheral_addr[4]	rf_port1_reg[4]	gpio_i[9]	p_interrupts[4]
21	dmem_addr[5]	imem_addr[5]	sram_d_muxed_addr[5]	sram_i_addr[5]	peripheral_addr[5]	rf_rs1[0]	gpio_i[10]	p_interrupts[5]
...	...	...	...	...	...	...	...	...
47	dmem_addr[31]	imem_addr[31]	sram_d_muxed_addr[31]	sram_i_addr[31]	peripheral_addr[31]	rf_rs1[26]	gpio_i[36]	p_interrupts[31]
48	dmem_req	imem_req	sram_d_muxed_req	sram_i_req	peripheral_req	rf_rs1[27]	gpio_i[37]	p_interrupts[32]
49	dmem_gnt	imem_gnt	sram_d_muxed_gnt	sram_i_gnt	peripheral_gnt	rf_rs1[28]	gpio_o[5]	p_interrupts[33]
50	dmem_we	imem_we	sram_d_muxed_we	sram_i_we	peripheral_we	rf_rs1[29]	gpio_o[6]	p_interrupts[34]
51	dmem_be[0]	imem_be[0]	sram_d_muxed_be[0]	sram_i_be[0]	peripheral_be[0]	rf_rs1[30]	gpio_o[7]	p_interrupts[35]
52	dmem_be[1]	imem_be[1]	sram_d_muxed_be[1]	sram_i_be[1]	peripheral_be[1]	rf_rs1[31]	gpio_o[8]	p_interrupts[36]
53	dmem_be[2]	imem_be[2]	sram_d_muxed_be[2]	sram_i_be[2]	peripheral_be[2]	rf_port2_reg[0]	gpio_o[9]	p_interrupts[37]
54	dmem_be[3]	imem_be[3]	sram_d_muxed_be[3]	sram_i_be[3]	peripheral_be[3]	rf_port2_reg[1]	gpio_o[10]	p_interrupts[38]
55	dmem_rvalid	imem_rvalid	sram_d_muxed_rvalid	sram_i_rvalid	peripheral_rvalid	rf_port2_reg[2]	gpio_o[11]	p_interrupts[39]
56	dmem_rdata[0]	imem_rdata[0]	sram_d_muxed_rdata[0]	sram_i_rdata[0]	peripheral_rdata[0]	rf_port2_reg[4]	gpio_o[12]	p_interrupts[40]
57	dmem_rdata[1]	imem_rdata[1]	sram_d_muxed_rdata[1]	sram_i_rdata[1]	peripheral_rdata[1]	rf_port2_reg[5]	gpio_o[13]	p_interrupts[41]
58	dmem_rdata[2]	imem_rdata[2]	sram_d_muxed_rdata[2]	sram_i_rdata[2]	peripheral_rdata[2]	rf_rs2[0]	gpio_o[14]	p_interrupts[42]
...	...	...	...	...	...	...	...	...
67	dmem_rdata[11]	imem_rdata[11]	sram_d_muxed_rdata[11]	sram_i_rdata[11]	peripheral_rdata[11]	rf_rs2[9]	gpio_o[23]	p_interrupts[51]
68	dmem_rdata[12]	imem_rdata[12]	sram_d_muxed_rdata[12]	sram_i_rdata[12]	peripheral_rdata[12]	rf_rs2[10]	gpio_o[24]	p_i_enable[0]
...	...	...	...	...	...	...	...	...
81	dmem_rdata[25]	imem_rdata[25]	sram_d_muxed_rdata[25]	sram_i_rdata[25]	peripheral_rdata[25]	rf_rs2[23]	gpio_o[37]	p_i_enable[13]
82	dmem_rdata[26]	imem_rdata[26]	sram_d_muxed_rdata[26]	sram_i_rdata[26]	peripheral_rdata[26]	rf_rs2[24]	gpio_oeb_no[5]	p_i_enable[14]
...	...	...	...	...	...	...	...	...
87	dmem_rdata[31]	imem_rdata[31]	sram_d_muxed_rdata[31]	sram_i_rdata[31]	peripheral_rdata[31]	rf_rs2[29]	gpio_oeb_no[10]	p_i_enable[19]
88	dmem_wdata[0]	imem_wdata[0]	sram_d_muxed_wdata[0]	sram_i_wdata[0]	peripheral_wdata[0]	rf_rs2[30]	gpio_oeb_no[11]	p_i_enable[20]
89	dmem_wdata[1]	imem_wdata[1]	sram_d_muxed_wdata[1]	sram_i_wdata[1]	peripheral_wdata[1]	rf_rs2[31]	gpio_oeb_no[12]	p_i_enable[21]
90	dmem_wdata[2]	imem_wdata[2]	sram_d_muxed_wdata[2]	sram_i_wdata[2]	peripheral_wdata[2]	rf_wr_reg[0]	gpio_oeb_no[13]	p_i_enable[22]
...	...	...	...	...	...	...	...	...
94	dmem_wdata[6]	imem_wdata[6]	sram_d_muxed_wdata[6]	sram_i_wdata[6]	peripheral_wdata[6]	rf_wr_reg[5]	gpio_oeb_no[17]	p_i_enable[26]
95	dmem_wdata[7]	imem_wdata[7]	sram_d_muxed_wdata[7]	sram_i_wdata[7]	peripheral_wdata[7]	rf_wr_data[0]	gpio_oeb_no[18]	p_i_enable[27]
...	...	...	...	...	...	...	...	...
114	dmem_wdata[26]	imem_wdata[26]	sram_d_muxed_wdata[26]	sram_i_wdata[26]	peripheral_wdata[26]	rf_wr_data[19]	gpio_oeb_no[37]	p_i_enable[46]
115	dmem_wdata[27]	imem_wdata[27]	sram_d_muxed_wdata[27]	sram_i_wdata[27]	peripheral_wdata[27]	rf_wr_data[20]	timer_intr	p_i_enable[47]
116	dmem_wdata[28]	imem_wdata[28]	sram_d_muxed_wdata[28]	sram_i_wdata[28]	peripheral_wdata[28]	rf_wr_data[21]	m_ext_intr	p_i_enable[48]
117	dmem_wdata[29]	imem_wdata[29]	sram_d_muxed_wdata[29]	sram_i_wdata[29]	peripheral_wdata[29]	rf_wr_data[22]	p_int_read	p_i_enable[49]
118	dmem_wdata[30]	imem_wdata[30]	sram_d_muxed_wdata[30]	sram_i_wdata[30]	peripheral_wdata[30]	rf_wr_data[23]	csr_busy	p_i_enable[50]
119	dmem_wdata[31]	imem_wdata[31]	sram_d_muxed_wdata[31]	sram_i_wdata[31]	peripheral_wdata[31]	rf_wr_data[24]	me_i_en	p_i_enable[51]
120	miu_illegal	mcause[0]	mcause[8]	mcause[16]	mcause[24]	rf_wr_data[25]	-	-
121	sram_illegal	mcause[1]	mcause[9]	mcause[17]	mcause[25]	rf_wr_data[26]	-	-
122	flash_illegal	mcause[2]	mcause[10]	mcause[18]	mcause[26]	rf_wr_data[27]	-	-
123	caravel_illegal	mcause[3]	mcause[11]	mcause[19]	mcause[27]	rf_wr_data[28]	-	-
124	illegal_access	mcause[4]	mcause[12]	mcause[20]	mcause[28]	rf_wr_data[29]	-	-
125	mem_err_int	mcause[5]	mcause[13]	mcause[21]	mcause[29]	rf_wr_data[30]	-	-
126	boot_sel	mcause[6]	mcause[14]	mcause[22]	mcause[30]	rf_wr_data[31]	-	-
127	copy_boot_sel	mcause[7]	mcause[15]	mcause[23]	mcause[31]	rf_wr_en	-	-

Pin Descriptions (QFN64 9x9 0.5)

Pin	Name	Description	Voltage min	Voltage nom	Voltage max
1	vssa2	Analog Ground		0
2	io25	IO 25	0	0.4 or (0.8 * vddio)	vddio
3	io26	IO 26	0	0.4 or (0.8 * vddio)	vddio
4	io27	IO 27	0	0.4 or (0.8 * vddio)	vddio
5	io28	IO 28	0	0.4 or (0.8 * vddio)	vddio
6	io29	IO 29	0	0.4 or (0.8 * vddio)	vddio
7	io30	IO 30	0	0.4 or (0.8 * vddio)	vddio
8	io31	IO 31	0	0.4 or (0.8 * vddio)	vddio
9	vdda2	Analog Supply Voltage		3.3
10	vssd2	Digital Ground		0
11	io32	IO 32	0	0.4 or (0.8 * vddio)	vddio
12	io33	IO 33	0	0.4 or (0.8 * vddio)	vddio
13	io34	IO 34	0	0.4 or (0.8 * vddio)	vddio
14	io35	IO 35	0	0.4 or (0.8 * vddio)	vddio
15	io36	IO 36	0	0.4 or (0.8 * vddio)	vddio
16	io37	IO 37	0	0.4 or (0.8 * vddio)	vddio
17	vddio1	IO Pad Supply Voltage	1.8	3.3	5
18	vccd	Core Voltage	1.62	1.8	1.98
19	N/C	No connect		-
20	vssa	Analog Ground		0
21	resetb	Digital Reset (Active Low)	0	> 0.8 * vddio	vddio
22	clock	10 MHz clock	0	0.4 or (0.8 * vddio)	vddio
23	vssd	Digital Ground		0
24	flash_csb	QSPI_0 Chip Select	0	0.4 or (0.8 * vddio)	vddio
25	flash_clk	QSPI_0 Clock	0	0.4 or (0.8 * vddio)	vddio
26	flash_io0	QSPI_0 D0	0	0.4 or (0.8 * vddio)	vddio
27	flash_io1	QSPI_0 D1	0	0.4 or (0.8 * vddio)	vddio
28	gpio	Single pin management GPIO	0	0.4 or (0.8 * vddio)	vddio
29	vssio	IO Pad Ground		0
30	vdda	Analog Supply Voltage		3.3
31	io0	JTAG	0	0.4 or (0.8 * vddio)	vddio
32	io1	SPI_0_SD0	0	0.4 or (0.8 * vddio)	vddio
33	io2	SPI_0_SDI	0	0.4 or (0.8 * vddio)	vddio
34	io3	SPI_0_CSB	0	0.4 or (0.8 * vddio)	vddio
35	io4	SPI_0_SCK	0	0.4 or (0.8 * vddio)	vddio
36	io5	CARP Core Copy Boot Select	0	0.4 or (0.8 * vddio)	vddio
37	io6	CARP Core Boot Select	0	0.4 or (0.8 * vddio)	vddio
38	vssa1	Analog Ground		0
39	vssd1	Digital Ground		0
40	vdda1	Analog Supply Voltage		3.3
41	io7	CARP Core Hard reset	0	0.4 or (0.8 * vddio)	vddio
42	io8	QSPI_1 Clock	0	0.4 or (0.8 * vddio)	vddio
43	io9	QSPI_1 Chip Select	0	0.4 or (0.8 * vddio)	vddio
44	io10	QSPI_1 D0	0	0.4 or (0.8 * vddio)	vddio
45	io11	QSPI_1 D1	0	0.4 or (0.8 * vddio)	vddio
46	io12	QSPI_1 D2	0	0.4 or (0.8 * vddio)	vddio
47	vdda1	Analog Supply Voltage		3.3
48	io13	QSPI_1 D3	0	0.4 or (0.8 * vddio)	vddio
49	vccd1	Core Voltage	1.8	3.3	5
50	io14	IO 14	0	0.4 or (0.8 * vddio)	vddio
51	io15	IO 15	0	0.4 or (0.8 * vddio)	vddio
52	vssa1	Analog Ground		0
53	io16	IO 16	0	0.4 or (0.8 * vddio)	vddio
54	io17	IO 17	0	0.4 or (0.8 * vddio)	vddio
55	io18	IO 18	0	0.4 or (0.8 * vddio)	vddio
56	vssio	IO Pad Ground		0
57	io19	IO 19	0	0.4 or (0.8 * vddio)	vddio
58	io20	IO 20	0	0.4 or (0.8 * vddio)	vddio
59	io21	IO 21	0	0.4 or (0.8 * vddio)	vddio
60	io22	IO 22	0	0.4 or (0.8 * vddio)	vddio
61	io23	IO 23	0	0.4 or (0.8 * vddio)	vddio
62	io24	IO 24	0	0.4 or (0.8 * vddio)	vddio
63	vccd2	Core Voltage	1.62	1.8	1.98
64	vddio2	IO Pad Supply Voltage	1.8	3.3	5