HD64570 Datasheet, PDF (62/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

Table 2.6 Bus Interface Lines
Pin Number
Symbol
RD*²
CP-84
4
FP-88
15
WR/RW 3
14
*2: Not connected
Input/
Output
Description
Input/ CPU modes 0, 1
output
Read: Indicates that the SCA is executing a
read cycle.
Master mode
Output line. When this line is
driven active low, the data bus
lines are used as inputs.
Slave mode
Input line. When this line is
driven active low, the data bus
lines are used as outputs.
Reset mode Input.
System stop Input.
mode
CPU modes 2, 3
Input/
output
*²
Always high. Leave
unconnected, or pull up to V_CC.
CPU modes 0, 1
Write: Indicates that the SCA is executing a
write cycle.
Master mode
Output line. When this line is
driven active low, the data bus
lines are used as outputs.
Slave mode
Input line. When this line is
driven active low, the data bus
lines are used as inputs.
Reset mode Input.
System stop Input.
mode
CPU modes 2, 3
Read/write: Indicates whether the SCA is
executing a read or write cycle, to control the
data direction.
Rev. 0, 07/98, page 46 of 453