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TDMA M3090/M3097:
Memory
WP*
Q1200
R1201
U1200
B+
WP*
Q1201
Description
A serial EEPROM(U1201) of 256K bytes is used for storage of the NAM information, authentication keys, phasing data, ESN, and memory. The EEPROM serial inter-
face to the microcontroller is a standard SPI-compatible interface.
U1250 is a 64K x 16 low voltage, low power SRAM. U1250 uses a parallel interface bus.
U1200 is a 512K x 8 flash EPROM. U1200 uses a parallel interface bus.
The WP* line is used during EPROM flash con ditions. When the EPROM is not being flash ed, WP* is at a low state. This condition w ill switch Q1200 off, thus, allowing
the gate of Q1201 to be pulled high. A high state at th e gate of Q1201 will switch Q1201 off, thus, not allow ing WP* from U1200 to be pulled high by B+.
During flashing condi tions, WP* is pulled high. This condition will switch Q1200 on , allowing the voltage at the gate of Q120 1 to drop. A lower vo ltage at the gate of
Q1201 will switch the transistor on. This condition will allow WP* from U1200 to be pulled high by B+.
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