MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 387

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

D.6.9 Parallel l/O Port A Configuration
To implement a DCE interface for the non-lSDN terminal, PA2 and PA5 should be config-
ured as general-purpose outputs (drive CTS and CD).
PA7 and PA8 should be configured as general-purpose outputs (drive SCP_EN and RE-
SET).
PA4 and PA6 may be configured either as general-purpose inputs or as dedicated modem
pins.
If a general-purpose input is chosen, the state of the terminal DTR and RTS lines will be
polled by application software by reading the parallel l/O data register.
If PA4 and PA6 are to be used as general-purpose inputs, the following registers should be
set:
If the dedicated mode is chosen, the software can use the delta mechanism of the SCC to
generate an interrupt upon any change in the state of RTS or DTR. In this case, the SCC
can be configured to use its CTS (connected to the terminal DTR line) and CD (connected
to the terminal RTS line) under automatic control or under software control by setting the
DIAG bits in the mode register.
If CTS2 (PA4) and CD2 (PA6) are to be used as dedicated pins, the following registers
should be set:
D.6.10 SCP Bus
The SCP (see Figure D-15) is an industry standard bus used for controlling and program-
ming external devices. The SCP is a four-wire bus consisting of transmit path, receive path,
associated clock, and enable signal (see Figure D-16). The clock determines the rate of the
exchange of data in both the transmit and receive directions, and the enable signal governs
when this exchange occurs.
MOTOROLA
PACNT
PADDR
PADAT
PACNT
PADDR
PADAT
Register
Register
$000B
$01A4
$005B
$01A4
Value
Value
Set PA0 PA1, and PA3 to the dedicated mode. (RXD2, TXD2, and TCLK2 connected to
SCC2.)
Set PA2, PA5, PA7, and PA8 as output pins. (RCLK2 and RTS2 are outputs.)
Will be set by the application software to drive PA2, PA5, PA7, and PA8 to the proper
state. Will be read to check DTR and RTS.
Set PA0, PA1, PA3, PA4, and PA5 to the dedicated mode. (RXD2, TXD2, TCLK2,
CTS2 and CD2 connected to SCC2.)
Set PA2, PA5, PA7, and PA8 as output pins. (RCLK2 and RTS2 are outputs.)
Will be set by the application software to drive PA2, PA5, PA7, and PA8 to the proper
state.
MC68302 USER’S MANUAL
Comments
Comments
MC68302 Applications
D-37