uart_csr.md

uart_csr

• byte_size
  • 32
• bus_width
  • 32

name	offset_address
rbr	0x00
thr	0x00
ier	0x04
iir	0x08
fcr	0x08
lcr	0x0c
mrc	0x10
lsr	0x14
msr	0x18
scratch	0x1c
dll	0x00
dlm	0x04

rbr

• offset_address
  • 0x00
• type
  • indirect
• index_bit_fields
  • lcr.dlab: 0
• comment
  • Receiver Buffer Register

name	bit_assignments	type	initial_value	reference	labels	comment
rbr	[7:0]	rotrg

thr

• offset_address
  • 0x00
• type
  • indirect
• index_bit_fields
  • lcr.dlab: 0
• comment
  • Transmitter Holding Register

name	bit_assignments	type	initial_value	reference	labels	comment
thr	[7:0]	wotrg	0xff

ier

• offset_address
  • 0x04
• type
  • indirect
• index_bit_fields
  • lcr.dlab: 0
• comment
  • Interrupt Enable Register

name	bit_assignments	type	initial_value	reference	labels	comment
erbfi	[0]	rw	0x0			Enable Received Data Available Interrupt 0: Disables Received Data Available Interrupts 1: Enables Received Data Available Interrupts
etbei	[1]	rw	0x0			Enable Transmitter Holding Register Empty Interrupt 0: Disables Transmitter Holding Register Empty Interrupts 1: Enables Transmitter Holding Register Interrupts
elsi	[2]	rw	0x0			Enable Receiver Line Status Interrupt 0: Disables Receiver Line Status Interrupts 1: Enables Receiver Line Status Interrupts
edssi	[3]	rw	0x0			Enable Modem Status Interrupt 0: Disables Modem Status Interrupts 1: Enables Modem Status Interrupts

iir

• offset_address
  • 0x08
• type
  • default
• comment
  • Interrupt Identification Register

name	bit_assignments	type	initial_value	reference	labels	comment
intpend	[0]	ro	0x1			0: Interrupt is pending 1: No interrupt is pending
intid2	[3:1]	ro	0x0			Interrupt ID 011: Receiver Line Status (Highest) 010: Received Data Available (Second) 110: Character Timeout (Second) 001: Transmitter Holding Register Empty (Third) 000: Modem Status (Fourth)

fcr

• offset_address
  • 0x08
• type
  • default
• comment
  • FIFO Control Register

name	bit_assignments	type	initial_value	reference	labels	comment
fifoen	[0]	wo	0x0			FIFO Enable 1: Enables FIFOs
rcvr_fifo_reset	[1]	w1trg				Receiver FIFO Reset 1: Resets RCVR FIFO
xmit_fifo_reset	[2]	w1trg				Transmitter FIFO Reset 1: Resets XMIT FIFO
dma_mode_select	[3]	wo	0x0			DMA Mode Select 0: Mode 0 1: Mode 1
rcvr_fifo_trigger_level	[7:6]	wo	0x0			RCVR FIFO Trigger Level 0b00: 1 byte 0b01: 4 bytes 0b10: 8 bytes 0b11: 14 bytes

lcr

• offset_address
  • 0x0c
• type
  • default
• comment
  • line control register

name	bit_assignments	type	initial_value	reference	labels	comment
wls	[1:0]	rw	0x3			Word Length Select 0b00: 5 bits/character 0b01: 6 bits/character 0b10: 7 bits/character 0b11: 8 bits/character
stb	[2]	rw	0x0			Number of Stop Bits 0: 1 Stop bit 1: 2 Stop bits or 1.5, if 5 bits/character selected
pen	[3]	rw	0x0			Parity Enable 1: Enables parity 0: Disables parity
eps	[4]	rw	0x0			Even Parity Select 1: Selects Even parity 0: Selects Odd parity
stick_parity	[5]	rw	0x0			Stick Parity 1: Stick Parity is enabled 0: Stick Parity is disabled
set_break	[6]	rw	0x0			Set Break 1: Enables break condition 0: Disables break condition
dlab	[7]	rw	0x0			Divisor Latch Access Bit. 1: Allows access to the Divisor Latch Registers and reading of the FIFO Control Register 0: Allows access to RBR, THR, IER and IIR registers

mrc

• offset_address
  • 0x10
• type
  • default
• comment
  • Modem Control Register

name	bit_assignments	type	initial_value	reference	labels	comment
dtr	[0]	rw	0x0			Data Terminal Ready 1: Drives DTRN Low 0: Drives DTRN High
rts	[1]	rw	0x0			Request To Send 1: Drives RTSN Low 0: Drives RTSN High
out1	[2]	rw	0x0			User Output 1 1: Drives OUT1N Low 0: Drives OUT1N High
out2	[3]	rw	0x0			User Output 2 1: Drives OUT1N Low 0: Drives OUT1N High
loop_back	[4]	rw	0x0			Loop Back 1: Enables loop back

lsr

• offset_address
  • 0x14
• type
  • default
• comment
  • Line Status Register

name	bit_assignments	type	initial_value	reference	labels	comment
dr	[0]	ro	0x0			Data Ready 0: All the data in RBR or FIFO is read 1: Complete incoming character has been received and transferred into the RBR of FIFO
oe	[1]	rotrg	0x0			Overrun Error
pe	[2]	rotrg	0x0			Parity Error
fe	[3]	rotrg	0x0			Framing Error
bi	[4]	rotrg	0x0			Break Interrupt
thre	[5]	ro	0x0			Transmitter Holding Register Empty 0: THR or Transmitter FIFO has data to transmit 1: THR and Transmitter FIFO are empty
temt	[6]	ro	0x0			Transmitter Empty: 0: THR or Transmitter shift register contains data 1: THR, Transmitter FIFO and Transmitter shift register are empty
error_in_rcvr_fifo	[7]	ro	0x0			RCVR FIFO contains at least one receiver error (Parity, Framing, Break condition)

msr

• offset_address
  • 0x18
• type
  • default
• comment
  • Modem Status Register

name	bit_assignments	type	initial_value	reference	labels	comment
dcts	[0]	rotrg	0x0			Delta Clear To Send Change in CTSN after last MSR read
ddsr	[1]	rotrg	0x0			Delta Data Set Ready Change in DSRN after last MSR read
teri	[2]	ro	0x0			Trailing Edge Ring Indicator RIN has changed from a Low to a High
ddcd	[3]	rotrg	0x0			Delta Data Carrier Detect Change in DCDN after last MSR read
cts	[4]	ro				Clear To Send Complement of CTSN input
dsr	[5]	ro				Data Set Ready Complement of DSRN input
ri	[6]	ro				Ring Indicator Complement of RIN input
dcd	[7]	ro				Data Carrier Detect Complement of DCDN input

scratch

• offset_address
  • 0x1c
• type
  • default
• comment
  • Scratch Register

name	bit_assignments	type	initial_value	reference	labels	comment
scratch	[7:0]	rw	0x00

dll

• offset_address
  • 0x00
• type
  • indirect
• index_bit_fields
  • lcr.dlab: 1
• comment
  • Divisor Latch (Least Significant Byte) Register

name	bit_assignments	type	initial_value	reference	labels	comment
dll	[7:0]	rw	default: 0x00

dlm

• offset_address
  • 0x04
• type
  • indirect
• index_bit_fields
  • lcr.dlab: 1
• comment
  • Divisor Latch (Most Significant Byte) Register

name	bit_assignments	type	initial_value	reference	labels	comment
dlm	[7:0]	rw	default: 0x00