Table 4-24 CSBOOT Base and Option Register Reset Values
Fields
Base Address
Block Size
Reset Values
$000000
1 Mbyte
Async/Sync Mode
Upper/Lower Byte
Read/Write
AS/DS
Asynchronous Mode
Both Bytes
Read/Write
AS
DSACK
13 Wait States
Supervisor/User Space
Any Level
Address Space
IPL
Autovector
Interrupt Vector Externally
4.9 Parallel Input/Output Ports
Fifteen SIM pins can be configured for general-purpose discrete input and output. Al-
though these pins are organized into two ports, port E and port F, function assignment
is by individual pin. Pin assignment registers, data direction registers, and data regis-
ters are used to implement discrete I/O.
4
4.9.1 Pin Assignment Registers
Bits in the port E and port F pin assignment registers (PEPAR and PFPAR) control the
functions of the pins in each port. Any bit set to one defines the corresponding pin as
a bus control signal. Any bit cleared to zero defines the corresponding pin as an I/O
pin.
4.9.2 Data Direction Registers
Bits in the port E and port F data direction registers (DDRE and DDRF) control the di-
rection of the pin drivers when the pins are configured as I/O. Any bit in a register set
to one configures the corresponding pin as an output. Any bit in a register cleared to
zero configures the corresponding pin as an input. These registers can be read or writ-
ten at any time. Writes have no effect.
4.9.3 Data Registers
A write to the port E and port F data registers (PORTE and PORTF) is stored in an
internal data latch, and if any pin in the corresponding port is configured as an output,
the value stored for that bit is driven out on the pin. A read of a data register returns
the value at the pin only if the pin is configured as a discrete input. Otherwise, the value
read is the value stored in the register. Both data registers can be accessed in two lo-
cations. Registers can be read or written at any time.
4.10 Factory Test
The test submodule supports scan-based testing of the various MCU modules. It is in-
tegrated into the SIM to support production test. Test submodule registers are intend-
ed for Motorola use only. Register names and addresses are provided in APPENDIX
D REGISTER SUMMARY to show the user that these addresses are occupied. The
QUOT pin is also used for factory test.
MC68331
SYSTEM INTEGRATION MODULE
MOTOROLA
4-57
USER’S MANUAL
MOTOROLA [ MOTOROLA ]
