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Les deux révisions précédentesRévision précédenteProchaine révision | Révision précédente | ||
back2root:ibm-pc-ms-dos:hardware:8250 [2023/01/06 23:07] – [Port 3FE - Modem Status Register - MSR (read only)] frater | back2root:ibm-pc-ms-dos:hardware:8250 [2023/02/23 20:55] (Version actuelle) – [UART - Universal Asynchronous Receiver/Transmitter] frater | ||
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Ligne 1: | Ligne 1: | ||
- | ====== UART - Universal Asynchronous Receiver/ | + | ====== |
{{tablelayout? | {{tablelayout? | ||
Ligne 26: | Ligne 26: | ||
| 4-7 |reserved (zero) | | 4-7 |reserved (zero) | ||
- | + | <WRAP round box> | |
- | - 16550 will interrupt if data exists in the FIFO and isn't read within the time it takes to receive four bytes or if no data is received within the time it takes to receive four bytes. | + | |
+ | </ | ||
===== Baud Rate Divisor Table ===== | ===== Baud Rate Divisor Table ===== | ||
{{tablelayout? | {{tablelayout? | ||
Ligne 167: | Ligne 168: | ||
| | | | ||
- | <WARP round box> | + | <WRAP round box> |
* Bits 0-3 are reset when the CPU reads the MSR | * Bits 0-3 are reset when the CPU reads the MSR | ||
* Bit 4 is the Modem Control Register RTS during loopback test | * Bit 4 is the Modem Control Register RTS during loopback test | ||
Ligne 177: | Ligne 178: | ||
Programming considerations: | Programming considerations: | ||
- | - 8250' | + | |
- | - 16550' | + | <WRAP round box> |
- | - PCs are capable of 38.4Kb, while AT's are capable of 115.2Kb | + | * 8250' |
- | - receiver checks only the first stop bit of each character regardless of the number of stop bits specified | + | |
- | - Older 8250 and 16450 UARTs may lose THRE interrupt if the THRE and Receive Data (RD) or the Line Status (LS) interrupts occur simultaneously during a full duplex transmission. | + | |
- | + | | |
- | 1. Disable/ | + | |
- | | + | |
- | | + | |
+ | | ||
| | ||
- | - data loss can occur without overrun or framing errors if the interrupts are serviced too slowly | + | * data loss can occur without overrun or framing errors if the interrupts are serviced too slowly |
- | - reserved bits are usually set to zero. Code should NOT rely on this being the case since future enhancement may use these bits | + | |
- | - see INT TABLE or IRQ for interrupt assignments | + | </ |
- | - see PORTS for COMx port assignment (3F8, | + | |
+ | * see [[back2root: | ||
+ | * see [[back2root: | ||