Difference between revisions of "UART RX"
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{{Port | {{Port | ||
|Number=$143B | |Number=$143B | ||
| + | |NumberDec=5179 | ||
| + | |PortMask=%0001 0100 0011 1011 | ||
|ShortDesc=Reads data from serial port, write sets the baudrate | |ShortDesc=Reads data from serial port, write sets the baudrate | ||
|Readable=Yes | |Readable=Yes | ||
|Writable=Yes | |Writable=Yes | ||
|Subsystem=UART | |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 {{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. | |
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| − | |||
| − | |||
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Latest revision as of 11:08, 4 May 2020
| Number | $143B |
|---|---|
| Decimal | 5179 |
| Short desc. | Reads data from serial port, write sets the baudrate |
| Bit Mask | %0001 0100 0011 1011 |
| Readable | Yes |
| Writable | Yes |
| 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 Video Timing Register ($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.