System-Protect Function; Control Registers; Misc System Protect Register; Misc Iram Size Register - Epson S1C17M20 Technical Manual

4 MEMORY AND BUS

4.5.1 System-Protect Function

The system-protect function protects control registers and bits from writings. They cannot be rewritten unless write
protection is removed by writing 0x0096 to the MSCPROT.PROT[15:0] bits. This function is provided to prevent
deadlock that may occur when a system-related register is altered by a runaway CPU. See "Control Registers" in
each peripheral circuit to identify the registers and bits with write protection.
Note: Once write protection is removed using the MSCPROT.PROT[15:0] bits, write enabled status is
maintained until write protection is applied again. After the registers/bits required have been al-
tered, apply write protection.

4.6 Control Registers

MISC System Protect Register

Register name Bit
MSCPROT 15–0 PROT[15:0]
Bits 15–0 PROT[15:0]
These bits protect the control registers related to the system against writings.
0x0096 (R/W):
Other than 0x0096 (R/W): Enable system protection
While the system protection is enabled, any data will not be written to the affected control bits (bits
with "WP" or "R/WP" appearing in the R/W column).

MISC IRAM Size Register

Register name Bit
MSCIRAMSZ 15–9 –
8
7–3 –
2–0 IRAMSZ[2:0]
Bits 15–3 Reserved
Bits 2–0 IRAMSZ[2:0]
These bits set the internal RAM size that can be used.

FLASHC Flash Read Cycle Register

Register name Bit
FLASHCWAIT 15–9 –
8
7–2 –
1–0 RDWAIT[1:0]
Bits 15–2 Reserved
Bits 1–0 RDWAIT[1:0]
These bits set the number of bus access cycles for reading from the Flash memory.
4-8
Bit name Initial
0x0000
Disable system protection
Bit name Initial
0x00
(reserved)
0x04
0x2
Table 4.6.1 Internal RAM Size Selections
MSCIRAMSZ.IRAMSZ[2:0] bits
0x7–0x3
0x2
0x1
0x0
Bit name Initial
0x00
(reserved)
0x00
0x1
Seiko Epson Corporation
Reset R/W
H0 R/W –
Reset R/W
– R –
0 H0 R/WP Always set to 0.
– R –
H0 R/WP
Internal RAM size
Reserved
2KB
1KB
512B
Reset R/W
– R –
0 H0 R/WP Always set to 0.
– R –
H0 R/WP
Remarks
Remarks
Remarks
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)