CIRCUIT DESCRIPTION
AUDIO/LOGIC DESCRIPTION (ALL MODELS)
This port is used to provide data communication with the computer used to program the transceiver. Connection is made via the front panel microphone connector. Another use for this port is data communication with an external data device such as a modem. Connection is made via connector J301. Communication cannot occur simultaneously over both of these paths.
Other General Purpose Inputs and Outputs
The
PA0 - Input for PTT signal from the microphone jack and W302/W312 option slot
PA1 - Input for the receive LTR or Call Guard data signal.
PA2 - Service request input from microcontroller U2 on the display board. This tells U101 that it has data to send on the SPI bus described previously.
PA3 - Input from the Option 1 pin of modem connector J301.
PA4/PA5 - Transmit LTR/Call Guard data output. These two outputs are used to create a pseudo sine- wave signal. See Section 3.5.4 for more information.
PA6 - Output for supervisory tones generated by the microcontroller such as busy and
PA7 - Input from the squelch circuit (see Section 3.4.4). When the received signal strength increases to the squelch threshold level, this input goes high. The microcontroller uses this information to determine when receive data is valid and to control audio muting.
3.3.2 MEMORY AND LATCH PROGRAMMING
RAM U107
When a data read or write to U107 occurs, the location in U107 is selected by address lines
and the data appears on data bus lines
22)low. Likewise, data is written by pulling the WE input (pin 27) low. See the U104 description which follows for more information.
Flash EPROM (U108)
As described in Section 3.3.1, U108 can store up to 128K bytes of data. The memory space is arranged as 32K of common code space and twelve 8K blocks of bank code space. The A15 line of the microcon- troller determines if common or bank code space is selected. When A15 is high, common space is selected, and when it is low, bank space is selected.
The A15 line controls the four
Therefore, when a data read or write to U108 occurs, the lower 13 bits of the address are specified by address lines
Read/Write Strobe Select
NAND gates U104C and U104B select the read and write signals applied to U107 and U108. When a memory read occurs, the R/W output of the microcon- troller goes high. This signal is inverted by U104C and applied to the OE of U108. When a memory write operation occurs, the R/W output of the microcon- troller goes low. U104B is then enabled by the high output of U104C, and the high E signal is inverted by U104B and applied to the WE pin of U107 and to U104D.
| February 2001 |
Part No. |