Z51F3220FNX Datasheet, PDF (259/312 Pages) Zilog, Inc. – Z8051 Series 8-Bit Microcontrollers

Z51F3220
Product Specification
USI1ST1 (USI1 Status Register 1: For UART and SPI mode) : F1H
7
6
5
4
3
DRE1
TXC1
RXC1
WAKE1
USI1RST
R/W
R/W
R
R/W
R/W
2
DOR1
R
1
0
FE1
PE1
R/W
R/W
Initial value : 80H
DRE1
TXC1
RXC1
WAKE1
USI1RST
DOR1
FE1
PE1
The DRE1 flag indicates if the transmit buffer (USI1DR) is ready to
receive new data. If DRE1 is ‘1’, the buffer is empty and ready to be
written. This flag can generate a DRE1 interrupt.
0
Transmit buffer is not empty.
1
Transmit buffer is empty.
This flag is set when the entire frame in the transmit shift register has
been shifted out and there is no new data currently present in the
transmit buffer. This flag is automatically cleared when the interrupt
service routine of a TXC1 interrupt is executed. This flag can generate a
TXC1 interrupt. This bit is automatically cleared.
0
Transmission is ongoing.
1
Transmit buffer is empty and the data in transmit shift register
are shifted out completely.
This flag is set when there are unread data in the receive buffer and
cleared when all the data in the receive buffer are read. The RXC1 flag
can be used to generate a RXC1 interrupt.
0
There is no data unread in the receive buffer
1
There are more than 1 data in the receive buffer
This flag is set when the RXD1 pin is detected low while the CPU is in
STOP mode. This flag can be used to generate a WAKE1 interrupt. This
bit is set only when in asynchronous mode of operation. This bit should
be cleared by program software. (only UART mode)
0
No WAKE interrupt is generated.
1
WAKE interrupt is generated
This is an internal reset and only has effect on USI1. Writing ‘1’ to this bit
initializes the internal logic of USI1 and this bit is automatically cleared to
‘0’.
0
No operation
1
Reset USI1
This bit is set if a Data OverRun occurs. While this bit is set, the
incoming data frame is ignored. This flag is valid until the receive buffer
is read.
0
No Data OverRun
1
Data OverRun detected
This bit is set if the first stop bit of next character in the receive buffer is
detected as ‘0’. This bit is valid until the receive buffer is read. (only
UART mode)
0
No Frame Error
1
Frame Error detected
This bit is set if the next character in the receive buffer has a Parity Error
to be received while Parity Checking is enabled. This bit is valid until the
receive buffer is read. (only UART mode)
0
No Parity Error
1
Parity Error detected
PS029902-0212
PRELIMINARY
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