Intel 80C196NU ユーザーズマニュアル
5-25
MEMORY PARTITIONS
5.5.3
Code Fetches in the 1-Mbyte Mode
CCR1.1 (the MODE64 bit) controls whether the device operates in 1-Mbyte or 64-Kbyte mode.
CCR1 is loaded with the contents of CCB1 at reset. When MODE64 is clear, the device operates
in 1-Mbyte mode. In this mode, code can execute from any page in the 1-Mbyte address space.
An extended jump, branch, or call instruction across pages changes the EPC value to the destina-
tion page. For example, assume that code is executing from page FFH. The following code seg-
ment branches to an external memory location in page 00H and continues execution.
CCR1 is loaded with the contents of CCB1 at reset. When MODE64 is clear, the device operates
in 1-Mbyte mode. In this mode, code can execute from any page in the 1-Mbyte address space.
An extended jump, branch, or call instruction across pages changes the EPC value to the destina-
tion page. For example, assume that code is executing from page FFH. The following code seg-
ment branches to an external memory location in page 00H and continues execution.
0FF2090H:
LD
TEMP,#12H
; code executing in page FFH
ST
TEMP,PORT1
; code executing in page FFH
EBR
003000H
; jump to location 3000H in page 00H
003000H:
ADD
TEMP,#50H
; code executing in page 00H
Code fetches are from external memory or internal memory, depending on the device, the instruc-
tion address, and the value of the EA# input.
tion address, and the value of the EA# input.
80C196NU:
Code executes from any page in external memory.
80C196NP:
For devices without internal nonvolatile memory, EA# must be tied low, and code executes from
any page in external memory.
any page in external memory.
83C196NP:
Code in all locations except FF2000–FF2FFFH executes from external memory.
Instruction fetches from FF2000–FF2FFFH are controlled by the EA# input:
•
If EA# is low, code executes from external memory.
•
If EA# is high, code executes from internal ROM.
Note that the EA# input functions only for the address range FF2000–FF2FFFH.
5.5.4
Code Fetches in the 64-Kbyte Mode
CCR1.1 (the MODE64 bit) controls whether the device operates in 1-Mbyte or 64-Kbyte mode.
CCR1 is loaded with the contents of CCB1 at reset. When MODE64 is set, the device operates in
64-Kbyte mode. In this mode, the EPC (Figure 5-7 on page 5-23) is fixed at FFH, which allows
instructions to execute from page FFH only. Extended jump, branch, and call instructions do not
function in the 64-Kbyte mode.
CCR1 is loaded with the contents of CCB1 at reset. When MODE64 is set, the device operates in
64-Kbyte mode. In this mode, the EPC (Figure 5-7 on page 5-23) is fixed at FFH, which allows
instructions to execute from page FFH only. Extended jump, branch, and call instructions do not
function in the 64-Kbyte mode.