Motorola M3097 Service Manual download pdf (Page 127)

TDMA M3090/M3097: Memory

B44

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 conditions, WP* is pulled high. This condition will switch Q1200 on, allowing the voltage at the gate of Q1201 to drop. A lower voltage at the gate of

Q1201 will switch the transistor on. This condition will allow WP* from U1200 to be pulled high by B+.

B+

WP*

Q1201

Q1200

U1200

WP*

R1201