DRM 85-C, DRM 85
09/2007
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Along with the main 3.3 V rail, the system crystal oscillator Y500 or Y501 starts,
selected by the logic state of U503. The system oscillator signal, MASTEROSC,
provides the Coldfire CPU clock signal which can be monitored at TP500.
Frequencies of 11.2896 MHz or 12.288 MHz are used by the CPU to furnish audio
sample rates of 44.1 kHz, 48 kHz and 32 kHz, and are selected as appropriate
by system software controlling the logic gate U503 which in turn enables the
corresponding oscillator IC.
Two additional memory elements are connected to the Coldfire CPU. U402 is a large
16 bit width Synchronous DRAM type Samsung K4S641633H providing
1 M x 16 bits x 4 banks of volatile storage and can be used by the system for
temporary storage of audio or other data.
U401 is an 8 bit width non-volatile NAND flash memory type Samsung
K9K4G08U0A providing up to 8 Gbits of storage space for audio data.The NAND
flash memory U402 also has a control signal NWP* to prevent accidental erasure
which must be in the high (H) state before storage or erasure can take place. This
memory is controlled by signals CLE, ALE, SRE, SWE and NAND* which are used to
latch either command signals, address signals, read, write and select
accordingly.
The intended purpose of NAND flash memory U401 is to store audio data
(recordings) and is intended to be used as a virtual disk-drive by way of file system
software running on the DRM target hardware.
3.3.3 Real time clock
Real Time Clock U203 type Ricoh R2051 K provides the CPU with a source of time
and date information upon request via an IIC connection. The time and date
information is used by the system software to add to the recorded files. U203 is
supplied by the EVER_3.3 V to run even if the device is switched off.
3.3.4 User Interfaces
Control elements - Switches
Rotary multifunction switch S500 along with additional switches S1, S2, and S3
located on the keyboard provide the input side of the user interface to the CPU.
Signals CW1, CW2, CCW1 and CCW2 are provided by S500 for menu navigation and
control in concert with signals SW1, SW2 and SW3 from the switches S1 to S3.
Assertion of either the SELECT signal (pushing the multifunction control in) or any
other control switch event causes either GPI05 or GPI06 to fall low and can be used
to generate a hardware interrupt condition to the system software.
USB
A USB interface U602 type Philips ISP1582 is used to provide connectivity to an
external personal computer. When connected to a PC the DRM enters a special state
for file transfer and all other processes (record or playback) are terminated in
difference to the 'disk drive' type operations possible over USB.
Stored files may be transferred across the USB connection at transfer speeds up to
12 Mbits/s (Full Speed) but using USB2.0 protocol set. In conjunction with a flash
file system suited to the NAND flash memory and USB protocol software, the DRM
appears to the remote PC as a removable disk drive.The connected state allows
operation direct from USB power with no batteries fitted.