Usb Bus; Figure 3-46. Patriot Ic (U100) Uart Configuration - Motorola ASTRO XTL 1500 Detailed Service Manual

Theory of Operation: Controller Section
3.14.6 RS-232 USB Bus
The XTL 1500 microcontroller in the Patriot IC (U100) has two internal UARTS that can be
configured for RS-232 data communication: UARTA and UARTB
Front connector
(50-pin) - J0401
Pins 25, 26
Pins 31, 31, 33, 34
Pins 27, 28, 29, 30
UARTA is configured for RS-232 data transmission by default, and its data transmission is routed
through an on-board RS-232 transceiver (U0305) to bring the data voltage levels up to EIA RS-232
standards before the data exits the front and rear of the radio. The U0305 is a two-driver, two-
receiver device, protected against ±15 kV electrostatic discharges.
For data output, UARTA transmits data from the microcontroller at 0-V and 2.85-V levels. This data is
sent on an asynchronous serial bus, which is routed to an on-board RS-232 transceiver (U0305) that
converts these low-voltage levels to -9 V and +9 V signal levels. This RS-232-formatted data is
routed out the front of the radio (J0401-27, J0401-28, J0401-29, J0401-30) and to the rear of the
radio (J0402-7, J0402-8, J0402-9, J0402-10).
For data input, U0305 can accept up to ±30-V signal levels. These high levels are converted inside
the U0305 down to 0-V and 5-V levels. Next these data levels are routed thru a buffer stage (U0303)
which lowers the data to 0-V and 2.85-V levels. This is the required voltage levels for the input into
the microcontroller.
This radio meets EIA compatibility with external data accessory devices. The naming scheme (see
Table 3-12) used for the microcontroller's RS-232 lines sometimes conflict with EIA RS-232 naming
schemes. This is due to the microcontroller's pin names versus I/O direction, compared to the EIA
pin names versus I/O direction. Therefore, a matching naming scheme has been developed. If the
pin is coming from the UART, the pin name has UART in the name. However, if you want to know
how the EIA standard identifies the pin, a chart exists that provides the naming conversion. The
shipping rear data cable automatically routes the pins according to the EIA standard, so interfacing
to external data devices, such as computers, is done correctly. The naming scheme information is
only needed when the rear connector is opened and the wires need to be identified for connection to
a custom device. Note that the correct interfacing of RS-232 lines is "output line" to "input line". For
example, the TX pin of one device connects to the RX pin of the other device, and the RTS pin of one
device connects to the CTS pin of the other device. Never connect TX to TX, RX to RX, and so on.
6815854H01-A
PATRIOT
U100
UART A
MUX
SWITCH
USB
XCVR
U0304
RS232
Boot_TX, Boot_RX
XCVR
U0305

Figure 3-46. Patriot IC (U100) UART Configuration

(Figure
UART B
SB9600
Circuit
BUS+, BUS-, BUSY, RESET
USB+, USB-, USB_PWR
TXD, RXD, CTS, RTS
3-69
3-46).
Rear connector
(26-pin) - J2
Pins 2, 3, 9, 8
Pins 7, 6, 12
Pins 4, 5, 10, 11
MAEPF-27702-O
June 15, 2005