SAM7S16 Atmel Corporation, SAM7S16 Datasheet - Page 102

• Manufacturer Part Number: SAM7S16
• Manufacturer: Atmel Corporation

Specifications of SAM7S16

• Flash (kbytes): 16 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 55 MHz
• Cpu: ARM7TDMI
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 21
• Ext Interrupts: 21
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Ssc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 384
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Self Program Memory: NO
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8/3.3
• Operating Voltage (vcc): 3.0 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 3
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: No

Memory Interface
3.9
3-32
Privileged mode access
ARM Limited usually recommends that if only privileged mode access is required from
a memory system then you are advised to use the nTRANS pin on the core. This signal
distinguishes between User and privileged accesses.
The reason that this is recommended is that if the Operating System (OS) accesses
memory on behalf of the current application then it must perform these accesses in User
mode. This is achieved using the LDRT and STRT instructions that set nTRANS
appropriately.
This measure avoids the possibility of a hacker deliberately passing an invalid pointer
to an OS and getting the OS to access this memory with privileged access. This
technique could otherwise be used by a hacker to enable the user application to access
any memory locations such as I/O space.
The least significant five bits of the CPSR are also output from the core as inverted
signals, nM[4:0]. These indicate the current processor mode as listed in Table 3-8.
The only time to use the nM[4:0] signals is for diagnostic and debug purposes.
Note
Copyright © 1994-2001. All rights reserved.
Table 3-8 Use of nM[4:0] to indicate current processor mode
M[4:0]
10000
10001
10010
10011
10111
11011
11111
nM[4:0]
01111
01110
01101
01100
01000
00100
00000
ARM DDI 0029G
Mode
User
FIQ
IRQ
Supervisor
Abort
Undefined
System