UART RX: Difference between revisions

Latest revision as of 11:08, 4 May 2020

Number	PortNumber::$143B
Decimal	NumberDec::5179
Short desc.	ShortDesc::Reads data from serial port, write sets the baudrate
Bit Mask	[[PortMask::%0001 0100 0011 1011]]
Readable	Readable::Yes
Writable	Writable::Yes
Subsystem	Subsystem::UART

Read a byte from the receive buffer. If the buffer is empty, 0 is returned.

Writes the lower 14-bits of the UART's prescalar value that determines baud rate

If bit 7 = 1

bits 6:0 = upper 7-bits of the 14-bit prescalar value

If bit 7 = 0

bits 6:0 = lower 7-bits of the 14-bit prescalar value

The UART's baud rate is determined by the prescalar according to this formula:

prescalar = Fsys / baudrate ; Fsys = system clock from {{#ask:

Eg: If the system is HDMI, nextreg 0x11 indicates that Fsys = 27000000. The prescalar for a baud rate of 115200 is 27000000 / 115200 = 234.

@@ Line 8: / Line 8: @@
 |Subsystem=UART
 }}
-Reads data from serial port. Write to this port sets the speed of serial communication, see the table:
+Read a byte from the receive buffer.  If the buffer is empty, 0 is returned.
-= 115200 (default at reset)
+Writes the lower 14-bits of the UART's prescalar value that determines baud rate
-= 57600
+: If bit 7 = 1
-= 38400
+::   bits 6:0 = upper 7-bits of the 14-bit prescalar value
-= 19200
+: If bit 7 = 0
-= 9600
+::   bits 6:0 = lower 7-bits of the 14-bit prescalar value
-= 4800
-= 2400
+The UART's baud rate is determined by the prescalar according to this formula:
+: prescalar = Fsys / baudrate ; Fsys = system clock from {{NextRegNo|$11}}
+Eg: If the system is HDMI, nextreg 0x11 indicates that Fsys = 27000000.  The prescalar for a baud rate of 115200 is 27000000 / 115200 = 234.