HD64570 HITACHI [Hitachi Semiconductor], HD64570 Datasheet - Page 180

• Manufacturer Part Number: HD64570
• Description: Serial Communications Adaptor
• Manufacturer: HITACHI [Hitachi Semiconductor]

TRBH Bits 7 0 (TRB15 TRB8/TRBH7 TRBH0: TX/RX Buffer High Byte (TRBH)): The
function of these bits is described below.
TRBL Bits 7 0 (TRB7 TRB0/TRBL7 TRBL0: TX/RX Buffer Low Byte (TRBL)): The
function of these bits is described below.
TRB read operation: Data is read from the receive buffer at TRB read in the procedure listed in
table 5.6 to table 5.8.
Table 5.6
Read Mode
Word read
Byte read
Table 5.7
Read Mode
Byte read
Rev. 0, 07/98, page 164 of 453
Asynchronous/Byte synchronous/Bit synchronous mode
Reading TRBH bits 7 0 reads a receive character from the receive buffer. If data is read from
these bits with the RXRDY bit of status register 0 (ST0) cleared to 0, the values are undefined
and subsequent operation is not guaranteed.
Writing TRBH bits 7 0 writes a transmit character to the transmit buffer. If data is written to
these bits with the TXRDY bit of ST0 cleared to 0, the write data and/or the data in the
transmit buffer may be lost.
Asynchronous/Byte synchronous/Bit synchronous mode
Reading TRBL bits 7 0 reads a receive character from the receive buffer. If data is read from
these bits, with the RXRDY bit of ST0 cleared to 0, the values are undefined and subsequent
operation is not guaranteed.
Writing TRBL bits 7 0 writes a transmit character to the transmit buffer. If data is written to
these bits, with the TXRDY bit of ST0 cleared to 0, the write data and/or the data in the
transmit buffer may be lost.
TRB Read Operation in CPU Mode 0
TRB Read Operation in CPU Mode 1
Accessed Register*
TRBH
TRBL
TRBH
TRBL
Accessed Register*
TRBH
TRBL
2
2
2 or More Bytes
Data 1*
Data 0*
Data 0*
Data 0*
2 or More Bytes
Data 0*
Data 0*
3
3
3
3
3
3
Data Byte Count in Receive Buffer*
Data Byte Count in Receive Buffer*
1 Byte
Undefined*
Data 0*
Data 0*
Data 0*
1 Byte
Data 0*
Data 0*
3
3
3
3
3
4
None
Undefined*
Undefined*
Undefined*
Undefined*
None
Undefined*
Undefined*
1
1
4
4
4
4
4
4