Motorola ASTRO XTSTM 4000 Detailed Service Manual Download

Page: 47 / 210

6871620L01-C

May 28, 2008

VOCON Section

3-21

3.2.4.1.1 Radio CE Connector Interface, Logic Level Translation, and Boot Data Path Control

The MAKO IC facilitates the interface to the radio's CE connector. Some of the CE connector lines
are at 5 V logic levels, so the MAKO IC converts those lines to GPIO voltage logic levels to interface
to the Patriot IC, as well as the encryption module. These lines include the SB9600 bus busy line
LH_BUSY, the RS 232 CTS and RTS lines, the RS232 data-out line, and the RS232 data-in line.

Another function that the MAKO IC provides with these lines is boot data path control. The boot data
path is as follows: boot data-in is multiplexed onto the RS232 data-out line while the boot data-out is
multiplexed with the SB9600 data line. This alternate data path is used only to Flash code into a
radio for the first time. The Patriot IC, through the SPI bus, controls this feature.

3.2.4.1.2 USB Transceiver

The USB transceiver, internal to the MAKO IC, is capable of transmitting and receiving serial data at
a rate of 12 megabits per second. The differential USB data comes from the CE connector, through
the 33-ohm resistors R1206 and R1207, and then to the USB1_DP and USB1_DM pins on the
MAKO IC. The USB receive interface from the MAKO IC to the Patriot IC is as follows: USB1_DP
routed to USB1_DAT_TXD, USB1_DM routed to USB2_SE0_VM_RXD.

The USB transmitter is enabled when the RS232_USB and USB_TXENAB signals are both driven
low by the Patriot IC. The single-ended data is output from the Patriot IC on the UTXD1_USB_VPO
pin and goes to the MAKO USB1_DAT_TXD pin. The data is driven out differentially on the
USB1_DP and USB1_DM, which go to the CE connector. The Patriot IC sends the single-ended
zero signal from pin USB_VMO to the MAKO IC USB1_SE0 pin.

When a USB cable is attached, pin CTS_CABLE_DET_5V is driven low and goes through level
translation in U701 and the output of CTS_CABLE_DET_3V is pulsed low and sent to the dual-core
processor. This line controls the USB and RS232 modes so that the data that is on those lines are
routed to the USB transceiver when a cable is detected. If a USB cable is not detected,
CTS_CABLE_DET_3V is high, the USB transceiver is put in suspend mode and the DP and DM pins
can now handle 5V tolerance for RS232 mode of operation.

3.2.4.1.3 One-Wire Support

New options and accessories that attach to the CE connector are identified by the Patriot IC using
the One-Wire protocol. The Option Select 2 pin on the CE connector also serves as the One-Wire
data pin. This signal is connected to the ONE_WIRE_OPT pin. This pin is connected to the dual-core
processor one-wire bus (ONE_WIRE_UP) through the MAKO IC internal isolation switch which is
controlled by the SPI commands sent from the dual-core processor. This isolation is needed to
prevent possible contention on the One-Wire bus when a smart battery is attached to the radio.

These new accessories are to GROUND pin CTS, of the CE connector. When this occurs, the MAKO
IC pin ONE_WIRE_OPT is asserted and the Patriot IC detects the change. The Patriot IC then
instructs the MAKO IC (via SPI) to connect the CE connector One-Wire line to the Patriot IC One-
Wire bus. In the case of the USB cable, the Patriot IC reads the One-Wire data from the cable and,
upon determining that a USB cable is attached, programs the MAKO IC for USB mode.

3.2.4.1.4 Watchdog Timer

The watchdog timer is a 125ms counter that is integrated into the MAKO IC and used during the
power down sequence. The MAKO IC will begin the power down sequence when a low-to-high
transition occurs on MECH_SW pin. Once this transition occurs, the MAKO IC begins the watchdog
timer. Upon expiration of the timer, the RESETX pin is asserted and all MAKO regulators are
shutdown. The dual-core processor can refresh the watchdog timer so that the software has enough
time to complete its tasks before the power is taken away completely.