MC68336/376
REGISTER SUMMARY
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
D-24
NOTE
Unless DATA14 is pulled down during reset, the MRM will be en-
abled. On generic MC68376 devices (blank ROM), the MRM is en-
abled at address $FF0000 (which is outside of the 1 Mbyte address
range of CSBOOT. On these devices, the MRM should be disabled
(since it is blank) by setting the STOP bit during system initialization.
BOOT— Boot ROM Control
Reset state of BOOT is specified at mask time. Bootstrap operation is overridden if
STOP = 1 at reset. This is a read-only bit.
0 = ROM responds to bootstrap word locations during reset vector fetch.
1 = ROM does not respond to bootstrap word locations during reset vector fetch.
LOCK — Lock Registers
The reset state of LOCK is specified at mask time. If the reset state of the LOCK is
zero, it can be set once after reset to allow protection of the registers after initialization.
Once the LOCK bit is set, it cannot be cleared again until after a reset. LOCK protects
the ASPC and WAIT fields, as well as the ROMBAL and ROMBAH registers. ASPC,
ROMBAL and ROMBAH are also protected by the STOP bit.
0 = Write lock disabled. Protected registers and fields can be written.
1 = Write lock enabled. Protected registers and fields cannot be written.
EMUL — Emulation Mode Control
0 = Normal ROM operation
The MC68376 does not support emulation mode, therefore, this bit reads zero. Writes
have no effect.
ASPC[1:0] — ROM Array Space
ASPC can be written only if LOCK = 0 and STOP = 1. ASPC1 places the ROM array
in either supervisor or unrestricted space. ASPC0 determines if the array resides in
program space only or with program and data space. The reset state of ASPC[1:0] is
specified at mask time. Table D-22 shows ASPC[1:0] encoding.
WAIT[1:0] — Wait States
WAIT[1:0] specifies the number of wait states inserted by the MRM during ROM array
accesses. The reset state of WAIT[1:0] is specified at mask time. WAIT[1:0] can be
written only if LOCK = 0 and STOP = 1. Table D-23 shows WAIT[1:0] encoding.
Table D-22 ROM Array Space Field
ASPC[1:0]
State Specified
00
Unrestricted program and data
01
Unrestricted program
10
Supervisor program and data
11
Supervisor program