cop8sgr5vej8xxx National Semiconductor Corporation, cop8sgr5vej8xxx Datasheet - Page 17

• Manufacturer Part Number: cop8sgr5vej8xxx
• Description: 8-bit Cmos Rom Based And Otp Microcontrollers With 8k To 32k Memory, Two Comparators And Usart
• Manufacturer: National Semiconductor Corporation

5.0 Functional Description
The instructions that utilize the stack pointer (SP) always
reference the stack as part of the base segment (Segment
0), regardless of the contents of the S register. The S register
is not changed by these instructions. Consequently, the
stack (used with subroutine linkage and interrupts) is always
located in the base segment. The stack pointer will be initial-
ized to point at data memory location 006F as a result of
reset.
The 128 bytes of RAM contained in the base segment are
split between the lower and upper base segments. The first
112 bytes of RAM are resident from address 0000 to 006F in
the lower base segment, while the remaining 16 bytes of
RAM represent the 16 data memory registers located at
addresses 00F0 to 00FF of the upper base segment. No
RAM is located at the upper sixteen addresses (0070 to
007F) of the lower base segment.
Additional RAM beyond these initial 128 bytes, however, will
always be memory mapped in groups of 128 bytes (or less)
at the data segment address extensions (XX00 to XX7F) of
the lower base segment. The additional 384 bytes of RAM in
this device are memory mapped at address locations 0100
to 017F, 0200 to 027F and 0300 to 037F hex.
Memory address ranges 0200 to 027F and 0300 to 037F are
unavailable on the COP8SGx5 and, if read, will return un-
derfined data.
5.5 ECON (CONFIGURATION) REGISTER
For compatibility with COP8SGx7 devices, mask options are
defined by an ECON Configuration Register which is pro-
grammed at the same time as the program code. Therefore,
the register is programmed at the same time as the program
memory.
(Continued)
FIGURE 7. RAM Organization
17
The format of the ECON register is as follows:
Bit 7
Bit 6
Bit 5
Bits 4, 3 = 0, 0 External CKI option selected. G7 is avail-
Bit 2
Bit 1
Bit 7
X
Bit 6
POR
= x
= 1
= 0
= 1
= 1
= 0
= 1
= 0, 1 R/C oscillator option selected. G7 is avail-
= 1, 0 Crystal oscillator with on-chip crystal bias
= 1, 1 Crystal oscillator with on-chip crystal bias
SECURITY
Bit 5
This is for factory test. The polarity is “Don’t
Care.”
Power-on reset enabled.
Power-on reset disabled.
Security enabled.
able as a HALT restart and/or general pur-
pose input. CKI is clock input.
able as a HALT restart and/or general pur-
pose input. CKI clock input. Internal R/C
components are supplied for maximum R/C
frequency.
resistor disabled. G7 (CKO) is the clock
generator output to crystal/resonator.
resistor enabled. G7 (CKO) is the clock gen-
erator output to crystal/resonator.
WATCHDOG feature disabled. G1 is a gen-
eral purpose I/O.
WATCHDOG feature enabled. G1 pin is
WATCHDOG output with weak pullup.
Force port I compatibility. Disable port F
outputs and pull-ups. This is intended for
compatibility with existing code and Mask
ROMMed devices only. This bit should be
CKI 2
Bit 4
CKI 1
Bit 3
WATCH
Bit 2
DOG
10131745
F-Port
Bit 1
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HALT
Bit 0