System Considerations
MC1321x Reference Manual, Rev. 1.6
3-4
Freescale Semiconductor
Figure 3-2. MC1321x Internal Functional Interconnects
3.4.1
System Reset
The MC1321x system does not have a master input that resets the entire SiP. Instead, the MCU reset input
RESET is the overriding reset and the reset input to the modem M_RST must be controlled by the MCU
(in Run Mode).
3.4.1.1
MCU Reset Input RESET
RESET is an active low dedicated pin with a pull-up device built in. It has input hysteresis, a high current
output driver, and no output slew rate control. Internal power-on reset and low-voltage reset circuitry
typically make external reset circuitry unnecessary. This pin is normally connected to the standard 6-pin
background debug connector so a development system can directly reset the MCU system. If desired, a
manual external reset can be added by supplying a simple switch to ground (pull RESET pin low to force
a reset).
Whenever any reset is initiated (whether from an external signal or from an internal system), the reset pin
is driven low for approximately 34 cycles of f
Self_reset
(which is the approximate 8 MHz startup clock),
released, and sampled again approximately 38 cycles of f
Self_reset
later. If reset was caused by an internal
source such as low-voltage reset or watchdog time-out, the circuitry expects the reset pin sample to return
a logic 1. If the pin is still low at this sample point, the reset is assumed to be from an external source. The
reset circuitry decodes the cause of reset and records it by setting a corresponding bit in the MCU system
control Reset Status Register (SRS).
Never connect any significant capacitance to the reset pin because that would interfere with the circuit and
sequence that detects the source of reset. If an external capacitance prevents the reset pin from rising to a
valid logic 1 before the reset sample point, all resets will appear to be external resets.
MCU reset operation and control is detailed in
Chapter 12, “MCU Resets, Interrupts, and System
M_RST
PTD3
M_IRQ
ATTN
RXTXEN
GPIO1/Out_of_Idle
GPIO2/CRC_Valid
MOSI
MISO
SPICLK
IRQ
PTD0
PTD1
PTE7
PTE6
PTE4/MOSI1
PTE3/MISO1
PTE5/SPSCK1
CE
PTE2/SS1
MODEM
MCU
RESET
46
44
43
11
MC1321x
Summary of Contents for freescale semiconductor MC13211
Page 40: ...MC1321x Pins and Connections MC1321x Reference Manual Rev 1 6 2 6 Freescale Semiconductor...
Page 166: ...Modem Modes of Operation MC1321x Reference Manual Rev 1 6 7 22 Freescale Semiconductor...
Page 172: ...Modem Interrupt Description MC1321x Reference Manual Rev 1 6 8 6 Freescale Semiconductor...
Page 186: ...MCU Modes of Operation MC1321x Reference Manual Rev 1 6 10 8 Freescale Semiconductor...
Page 208: ...MCU Memory MC1321x Reference Manual Rev 1 6 11 22 Freescale Semiconductor...
Page 244: ...MCU Parallel Input Output MC1321x Reference Manual Rev 1 6 13 20 Freescale Semiconductor...
Page 288: ...MCU Central Processor Unit CPU MC1321x Reference Manual Rev 1 6 15 20 Freescale Semiconductor...
Page 308: ...MCU Timer PWM TPM Module MC1321x Reference Manual Rev 1 6 17 16 Freescale Semiconductor...
Page 338: ...Inter Integrated Circuit IIC MC1321x Reference Manual Rev 1 6 19 14 Freescale Semiconductor...
Page 372: ...Development Support MC1321x Reference Manual Rev 1 6 21 20 Freescale Semiconductor...