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User’s Manual 171

Table 12-12. Status Register Clocked Serial (Ports A-D only)

Serial Port x Status Register (SASR) (Address = 0xC3)

(SBSR) (Address = 0xD3)

(SCSR) (Address = 0xE3)

(SDSR) (Address = 0xF3)

Bit(s) Value Description (Clocked serial mode only)

0 The receive data register is empty

There is a byte in the receive buffer. The serial port will request an interrupt

while this bit is set. The interrupt is cleared when the receive buffer is empty.

6 0 This bit is always zero in clocked serial mode.

0 The receive buffer was not overrun.

1 The receive buffer was overrun. This bit is cleared by reading the receive buffer.

4 0 This bit is always zero in clocked serial mode.

0 The transmit buffer is empty.

The transmit buffer is not empty. The serial port will request an interrupt when

the transmitter takes a byte from the transmit buffer. Transmit interrupts are

cleared when the transmit buffer is written, or any value (which will be ignored)

is written to this register.

0 The transmitter is idle.

The transmitter is sending a byte. An interrupt is generated when the transmitter

clears this bit, which occurs only if the transmitter is ready to start sending

another byte but the transmit buffer is empty.

1:0 00 These bits are always zero in clocked serial mode.

1 2 ... 175 176 177 178 179 180 181 182 183 184 185 ... 348 349

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Jameco-electronics Rabbit 3000 Manuale Utente Pagina 180