SAM7S16 Atmel Corporation, SAM7S16 Datasheet - Page 94

• 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
3.6.2
3.6.3
3-24
ABORT
Byte latch enables
ABORT indicates that a memory transaction failed to complete successfully. ABORT
is sampled at the end of the bus cycle during S-cycles and N-cycles.
If ABORT is asserted on a data access, it causes the processor to take the Data Abort
trap. If it is asserted on an opcode fetch, the abort is tracked down the pipeline, and the
Prefetch Abort trap is taken if the instruction is executed.
ABORT can be used by a memory management system to implement, for example, a
basic memory protection scheme, or a demand-paged virtual memory system.
To ease the connection of the ARM7TDMI core to sub-word sized memory systems,
input data and instructions can be latched on a byte-by-byte basis. This is achieved by
the use of the BL[3:0] signal as follows:
•
•
•
•
It is recommended that BL[3:0] is tied HIGH in new designs and word values from
narrow memory systems are latched onto latches that are external to the ARM7TDMI
core.
In a memory system that only contains word-wide memory, BL[3:0] can be tied HIGH.
For sub-word wide memory systems, the BL[3:0] signals are used to latch the data as it
is read out of memory. For example, a word access to halfword wide memory must take
place in two memory cycles:
•
•
In Figure 3-18 on page 3-25, a word access is performed from halfword wide memory
in two cycles:
•
•
BL[3] controls the latching of the data present on D[31:24]
BL[2] controls the latching of the data present on D[23:16]
BL[1] controls the latching of the data present on D[15:8]
BL[0] controls the latching of the data present on D[7:0].
in the first cycle, the data for D[15:0] is obtained from the memory and latched
into the core on the falling edge of MCLK when BL[1:0] are both HIGH.
in the second cycle, the data for D[31:16] is latched into the core on the falling
edge of MCLK when BL[3:2] are both HIGH and BL[1:0] are both LOW.
in the first cycle, the read data is applied to the lower half of the bus
in the second cycle, the read data is applied to the upper half of the bus.
Note
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ARM DDI 0029G