UART: Difference between revisions
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m (Register formatting.) |
(Splits Serial Data into Serial Receive Data and Serial Transmit Data) |
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This allows for an effective maximum transfer speed of 960 or 3840 bytes per second, respectively. | This allows for an effective maximum transfer speed of 960 or 3840 bytes per second, respectively. | ||
The hardware also features | The hardware also features one-byte transmit and receive buffers, which allow for a slight delay in code when handling data to/from the console. | ||
== Interrupts == | == Interrupts == | ||
| Line 12: | Line 12: | ||
The UART features two interrupts: | The UART features two interrupts: | ||
* UART Send Ready - constantly active while the transmit buffer is empty (Serial | * UART Send Ready - constantly active while the transmit buffer is empty (Serial Status bit 2), | ||
* UART Receive Ready - constantly active while the receive buffer contains a byte (Serial | * UART Receive Ready - constantly active while the receive buffer contains a byte (Serial Status bit 0). | ||
== I/O ports == | == I/O ports == | ||
=== Serial Data === | {{Anchor|Serial Receive Data}} | ||
=== Serial Receive Data ($B1 read) === | |||
<pre> | <pre> | ||
| Line 24: | Line 25: | ||
dddd dddd | dddd dddd | ||
|||| |||| | |||| |||| | ||
++++-++++- | ++++-++++- Receive buffer value | ||
</pre> | </pre> | ||
=== Serial | {{Anchor|Serial Transmit Data}} | ||
=== Serial Transmit Data ($B1 write) === | |||
<pre> | <pre> | ||
7 bit 0 | 7 bit 0 | ||
---- ---- | ---- ---- | ||
dddd dddd | |||
|| | |||| |||| | ||
|| | ++++-++++- Transmit buffer value | ||
|| | </pre> | ||
|| | |||
{{Anchor|Serial Status}} | |||
=== Serial Status ($B3 read) === | |||
<pre> | |||
7 bit 0 | |||
---- ---- | |||
eb.. .tor | |||
|| ||| | |||
|| ||+- 1 if the receive buffer contains a byte | |||
|| |+-- 1 on overrun (receive buffer overflow) | |||
|| +--- 1 if the transmit buffer is empty (can transmit another byte) | |||
|+-------- UART speed: 0 = 9600 bps, 1 = 38400 bps | |||
+--------- UART enable: 0 = off, 1 = on | |||
</pre> | |||
{{Anchor|Serial Control}} | |||
=== Serial Control ($B3 write) === | |||
<pre> | |||
7 bit 0 | |||
---- ---- | |||
ebO. .... | |||
||| | |||
||+------- Write 1 to reset overrun | ||+------- Write 1 to reset overrun | ||
|+-------- UART speed: 0 = 9600 bps, 1 = 38400 bps | |+-------- UART speed: 0 = 9600 bps, 1 = 38400 bps | ||
+--------- UART enable: 0 = off, 1 = on | +--------- UART enable: 0 = off, 1 = on | ||
</pre> | </pre> | ||
Latest revision as of 12:05, 22 August 2023
The WonderSwan's EXT port features an UART operating with the following configuration:
- 9,600 or 38,400 bps (bauds per second),
- 8N1 (8 data bits followed by 1 stop bit, no parity).
This allows for an effective maximum transfer speed of 960 or 3840 bytes per second, respectively.
The hardware also features one-byte transmit and receive buffers, which allow for a slight delay in code when handling data to/from the console.
Interrupts
The UART features two interrupts:
- UART Send Ready - constantly active while the transmit buffer is empty (Serial Status bit 2),
- UART Receive Ready - constantly active while the receive buffer contains a byte (Serial Status bit 0).
I/O ports
Serial Receive Data ($B1 read)
7 bit 0 ---- ---- dddd dddd |||| |||| ++++-++++- Receive buffer value
Serial Transmit Data ($B1 write)
7 bit 0 ---- ---- dddd dddd |||| |||| ++++-++++- Transmit buffer value
Serial Status ($B3 read)
7 bit 0 ---- ---- eb.. .tor || ||| || ||+- 1 if the receive buffer contains a byte || |+-- 1 on overrun (receive buffer overflow) || +--- 1 if the transmit buffer is empty (can transmit another byte) |+-------- UART speed: 0 = 9600 bps, 1 = 38400 bps +--------- UART enable: 0 = off, 1 = on
Serial Control ($B3 write)
7 bit 0 ---- ---- ebO. .... ||| ||+------- Write 1 to reset overrun |+-------- UART speed: 0 = 9600 bps, 1 = 38400 bps +--------- UART enable: 0 = off, 1 = on
