SYSTEM INTEGRATION MODULE
M68HC16 Z SERIES
5-70
USER’S MANUAL
However, the internal pull-up driver can be overcome by bus loading effects. To en-
sure a particular configuration out of reset, use an active device to put DATA0 in a
known state during reset.
The base address field in the boot chip-select base address register CSBARBT has a
reset value of all zeros, so that when the initial access to address $000000 is made,
an address match occurs, and the CSBOOT signal is asserted. The block size field in
CSBARBT has a reset value of 512 Kbytes.
shows CSBOOT reset values.
5.10 Parallel Input/Output Ports
Sixteen 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. PE3 is not connected to a pin. PE3 returns zero when read and
writes have no effect. Pin assignment registers, data direction registers, and data reg-
isters are used to implement discrete I/O.
5.10.1 Pin Assignment Registers
Bits in the port E and port F pin assignment registers (PEPAR and PFPAR) control the
functions of the pins on 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. PEPA3 returns one when read, and writes have no effect.
5.10.2 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. DDE3 returns zero when read. Writes have no effect.
Table 5-26 CSBOOT Base and Option Register Reset Values
Fields
Reset Values
Base address
$000000
Block size
512 Kbyte
Async/sync mode
Asynchronous mode
Upper/lower byte
Both bytes
Read/write
Read/write
AS/DS
AS
DSACK
13 wait states
Address space
Supervisor space
IPL
1
NOTES:
1. These fields are not used unless “Address space” is
set to CPU space.
Any level
Autovector
Interrupt vector externally
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..