M42800A Atmel Corporation, M42800A Datasheet - Page 240
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M42800A
Manufacturer Part Number
M42800A
Description
Manufacturer
Atmel Corporation
Datasheets
1.M40800.pdf
(284 pages)
2.M40800.pdf
(153 pages)
3.M42800A.pdf
(224 pages)
4.M42800A.pdf
(27 pages)
Specifications of M42800A
Flash (kbytes)
0 Kbytes
Pin Count
144
Max. Operating Frequency
33 MHz
Cpu
ARM7TDMI
Hardware Qtouch Acquisition
No
Max I/o Pins
54
Ext Interrupts
54
Usb Speed
No
Usb Interface
No
Spi
2
Uart
2
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
8
Self Program Memory
NO
External Bus Interface
1
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
3.3/5.0
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
6
Input Capture Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
No
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Debug in Depth
B.7
B.7.1
B-22
The ARM7TDMI core clocks
Clock switch during debug
The ARM7TDMI core has two clocks:
•
•
During normal operation, the core is clocked by MCLK and internal logic holds DCLK
LOW. When the ARM7TDMI core is in the debug state, the core is clocked by DCLK
under control of the TAP state machine and MCLK can free-run. The selected clock is
output on the signal ECLK for use by the external system.
When the CPU core is being debugged and is running from DCLK, nWAIT has no
effect.
When the ARM7TDMI core enters debug state, it must switch from MCLK to DCLK.
This is handled automatically by logic in the ARM7TDMI core. On entry to debug state,
the core asserts DBGACK in the HIGH phase of MCLK. The switch between the two
clocks occurs on the next falling edge of MCLK. This is shown in Figure B-5.
The ARM7TDMI core is forced to use DCLK as the primary clock until debugging is
complete. On exit from debug, the core must be enabled to synchronize back to MCLK.
This must be done in the following sequence:
1.
the memory clock, MCLK
an internally TCK generated clock, DCLK.
The final instruction of the debug sequence must be shifted into the data bus scan
chain and clocked in by asserting DCLK.
Note
DBGACK
Copyright © 1994-2001. All rights reserved.
MCLK
DCLK
ECLK
Figure B-5 Clock switching on entry to debug state
Multiplexer
switching point
ARM DDI 0029G
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