MOTOROLA
116
MC68HC16Y1
MC68HC16Y1TS/D
9 Masked ROM Module
The masked ROM module (MRM) is designed to be used with the entire line of Motorola modular mi-
crocontrollers. The MRM consists of a fixed-location control register block and a memory array. Config-
uration information is contained in the register block. Default reset base address of the array in the
system address map is specified by the customer, but the array may be remapped to other addresses.
In addition to the array base address, the register block contains operating parameters, bootstrap code,
and ROM verification information. An address map of the register block follows.
Y = M111, where M is the state of the modmap bit in the module configuration register of the
single-chip integration module. In an MC68HC16Y1 system, M must always be set to one.
The ROM array in the MC68HC16Y1 contains 48 Kbytes. It is arranged in 16-bit words, and is accessed
via the intermodule bus. Bytes, words, and misaligned words can be accessed. Access time depends
upon the number of wait states specified at mask programming time, but can be as fast as two system
clocks for byte and aligned words. The MRM also responds to back-to-back IMB accesses to provide
two bus cycle long word access.
The array base address must be on a 64 Kbyte boundary, must not overlap the control registers of other
microcontroller modules, and should not overlap the control register block. The array occupies the low-
order locations in the 64 Kbyte block —accesses to the remaining 16 Kbytes of unimplemented loca-
tions in the block are ignored by the MRM, allowing other system resources or external devices to re-
spond to the access. If the array is mapped to overlap the control registers of other modules, accesses
to those registers will be indeterminate; if the array is mapped to overlap the MRM control registers,
accesses to the registers are still possible, but accesses to the overlapping 32 bytes of ROM bytes will
be ignored.
The primary function of the MRM is to serve as nonvolatile memory for the microcontroller. It can be
configured to support system bootstrap during reset. The CPU16 in the MC68HC16Y1 differentiates be-
tween program space accesses and data space accesses. The MRM array can be used for program
code only, or for both program code and data. The MRM can also be programmed to insert wait states
to accommodate migration from slower external development memory to the ROM array without retim-
ing.
Table 32 MRM Control Register Address Map
Address
$YFF820
$YFF822
$YFF824
$YFF826
$YFF828
$YFF82A
$YFF82C
$YFF82E
$YFF830
$YFF832
$YFF834
$YFF836
$YFF838
$YFF83A
$YFF83C
$YFF83E
15
8 7
0
MASKED ROM MODULE CONFIGURATION REGISTER (MRMCR)
NOT IMPLEMENTED
ARRAY BASE ADDRESS REGISTER HIGH (ROMBAH)
ARRAY BASE ADDRESS REGISTER LOW (ROMBAL)
ROM SIGNATURE HIGH REGISTER (RSIGHI)
ROM SIGNATURE LOW REGISTER (RSIGLO)
NOT IMPLEMENTED
NOT IMPLEMENTED
ROM BOOTSTRAP WORD 0 (ROMBS0)
ROM BOOTSTRAP WORD 1 (ROMBS1)
ROM BOOTSTRAP WORD 2 (ROMBS2)
ROM BOOTSTRAP WORD 3 (ROMBS3)
NOT IMPLEMENTED
NOT IMPLEMENTED
NOT IMPLEMENTED
NOT IMPLEMENTED