Datasheet

MAX9260 Evaluation Kit
Evaluates: MAX9260
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Detailed Description of Firmware
The DS89C450 microcontroller (U12) runs custom firm-
ware, which ensures that no breaks occur within reg-
ister read/write commands. The firmware records 9-bit
even-parity data received from the USB interface while
RTS is set, and plays back the 9-bit data with 1.5 stop
bits timing when RTS is cleared. Data received from the
MAX9260 is relayed to USB immediately.
The audio chips are initialized by an I
2
C command
sequence sent by the firmware when the microcon-
troller is reset. The same firmware runs on both the
MAX9259 and MAX9260 EV kit boards, so this initializa-
tion sequence covers both the S/PDIF-to-I
2
S converter
and the MAX9850 I
2
S stereo audio DAC. Pressing switch
SW122 resets the microcontroller, resending the audio
I
2
C initialization commands.
The firmware also supports a small set of commands,
available when RTS is clear. Since all register read/
write requests are sent with RTS set, there is no conflict
between register data and firmware commands. These
firmware commands are issued automatically by the
MAX9259 EV kit software GUI. The following information
is provided for reference only.
Firmware command “?” prints the firmware version ban-
ner message and brief command list.
Firmware command “B” changes the baud rate by
changing the internal TH1 baud-rate divisor. Refer to
firmware help command “?” for details. Pressing switch
SW122 resets the USB baud rate to 921600 baud. The
software GUI automatically sends the baud-rate change
command.
Firmware command “T” supports waking up the MAX9259
from the MAX9260 side of the link. Command “T” per-
forms a dummy read, followed by a delay on the order
of 1ms to 8ms, and finally writes a register value. For
example, send “T810558800483” to read from device
address 0x81 register 0x05, delay 4ms, then write to
device address 0x80 register 0x04 data 0x83. This is
the MAX9259 wake-up sequence for the default device
addresses. The software GUI automatically sends this
command when the Wake Up MAX9259 button is
pressed.
Table 1. Jumper Descriptions
JUMPER SIGNAL SHUNT POSITION DESCRIPTION
JU1 CDS
1-2
CDS = high; ECU attached to MAX9260; connect USB to MAX9260
EV kit
2-3* CDS = low; optional peripheral attached to MAX9260
Open Reserved
SW1 MS
1-2
(toggle switch up)
MS = high; full-duplex bypass mode; device registers not acces-
sible
2-3
(toggle switch down)
MS = low; half-duplex base mode; required when writing to device
registers or when using an external I
2
C peripheral
JU2 BWS
1-2* BWS = high
2-3 BWS = low
JU3 ES
1-2* ES = high
2-3 ES = low
JU4 DRS
1-2* DRS = high
2-3 DRS = low
JU5 SSEN
1-2* SSEN = high
2-3 SSEN = low
JU6
PWDN
1-2*
PWDN = high
2-3
PWDN = low