Jameco Electronics 3000 ユーザーズマニュアル
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)
7
0
The receive data register is empty
1
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.
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.
5
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.
3
0
The transmit buffer is empty.
1
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.
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.
2
0
The transmitter is idle.
1
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.
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.