6881076C25-E September 5, 2008
Theory of Operation: ASTRO Spectra VOCON Board 3-23
The same UART internal to the MCU is used in the controller bootstrap mode of operation. This
mode is used primarily in downloading new program code to the FLASH ROMs on the VOCON
board. In this mode, the MCU accepts special code downloaded at 7200 baud through the SCI bus
instead of operating from program code resident in its ROMs.
Figure 3-11. Host SB9600 and RS232 Ports
A voltage greater than 10 Vdc applied to J501-31 (Vpp) will trip the circuit comprising Q203, Q204,
and VR207. This circuit sets the MODA and MODB pins of the MCU to bootstrap mode (logic 0,0). If
the Vpp voltage is raised to 12 Vdc required on the FLASH devices for programming, the circuit
comprising VR208, Q211, and Q208 will trip, supplying Vpp to the FLASH devices, U205 and U404.
The ASTRO Digital Spectra radio has an additional asynchronous serial bus which utilizes RS232
bus protocol. This bus utilizes the UART in the SLIC IC (U206). It consists of TX/RS232 (J501-43),
RX/RS232 (J501-50), CTS/RS232 (J501-5), and RTS/RS232 (J501-42). It is a four-wire duplex bus
used to connect to external data devices.
PD1 (TXD)
PD0 (RXD)
HC11F1
U204
J501-18
H_DATA/BOOT_DATA_OUT
J501-43
RS232_DATA_OUT
BOOT_DATA_IN
BOOT_DATA_OUT
J501-20
SB9600_BUSY
PA3
J501-42
RTS_IN*
J501-50
RS232_DATA_IN
J501-5
CTSOUT*
RXDIN
PJ2
PJ3
RTSBIN
SLIC IV
U206
MAEPF-25109-O
J501-17
BOOT_DATA_IN
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