Chapter 3 – Electrical Characteristics
Multi-Tech Systems, Inc. MMCModem GPRS Developer’s Guide (S000445D)
27
SPI Bus Electrical Interface
The SPI bus includes a CLK signal, an I/O signal and an EN signal complying with SPI bus
standard. The maximum speed transfer is 3.25Mb/s.
SPI Bus Pin Description
Signal
Pin #
I/O
I/O Type*
Description
SPI_CLK
44
O
1X
SPI Serial Clock
SPI_IO 43 I/O CMOS/1X SPI
Data
SPI_EN
42
O
1X
SPI Enable
* See “Operating Conditions” in section on the
50-pin Connector Description
.
Keypad Electrical Interface
This interface provides 10 connections: 5 rows (R0 to R4) and 5 columns (C0 to C4).
The scanning is a digital one, and the de-bouncing is done in the integrated modem. No
discrete components like R, C (Resistor, Capacitor) are needed. It is possible to scan the
column and rows using the AT+CMER command. See AT Command manual for more
details.
Keypad Interface Pin Description
Signal
Pin #
I/O
I/O Type*
Description
ROW0
39
I/O
CMOS / 1X
Row scan
ROW1
40
I/O
CMOS / 1X
Row scan
ROW2
37
I/O
CMOS / 1X
Row scan
ROW3
38
I/O
CMOS / 1X
Row scan
ROW4
35
I/O
CMOS / 1X
Row scan
COL0
36
I/O
CMOS / 1X
Column scan
COL1
33
I/O
CMOS / 1X
Column scan
COL2
34
I/O
CMOS / 1X
Column scan
COL3
31
I/O
CMOS / 1X
Column scan
COL4
32
I/O
CMOS / 1X
Column scan
* See “Operating Conditions” in section on the
50-pin Connector Description
.
