mc68hc705c9a Freescale Semiconductor, Inc, mc68hc705c9a Datasheet - Page 18

• Manufacturer Part Number: mc68hc705c9a
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

General Description
1.5 Software-Programmable Options (MC68HC05C9A Mode Only)
The C9A option register (OR), shown in
register contains the programmable bits for the following options:
This register must be written to by user software during operation of the microcontroller.
RAM0 — Random Access Memory Control Bit 0
RAM1— Random Access Memory Control Bit 1
IRQ — Interrupt Request Bit
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This read/write bit selects between RAM or EPROM in location $0020 to $004F. This bit can be read
or written at any time.
This read/write bit selects between RAM or EPROM in location $0100 to $017F. This bit can be read
or written at any time.
This bit selects between an edge-triggered only or edge- and level- triggered external interrupt pin.
This bit is set by reset, but can be cleared by software. This bit can be written only once.
1 = RAM selected
0 = EPROM selected
1 = RAM selected
0 = EPROM selected
1 = Edge and level interrupt option selected
0 = Edge-only interrupt option selected
Map two different areas of memory between RAM and EPROM, one of 48 bytes and one of 128
bytes
Edge-triggered only or edge- and level-triggered external interrupt (IRQ pin and any port B pin
configured for interrupt)
$3FDF
Reset:
Read:
Write:
RAM0
Bit 7
0
MC68HC05C9A Advance Information Data Sheet, Rev. 4.1
= Unimplemented
RAM1
6
0
Figure 1-4. C9A Option Register
Figure
5
0
1-4, is enabled only if configured in C9A mode. This
4
0
3
0
2
0
IRQ
1
1
Freescale Semiconductor
Bit 0
0