Product Specs

Table Of Contents
43 PDM Pulse density modulation interface
Page
440
The PSEL.CLK and PSEL.DIN registers and their configurations are only used as long as the PDM module
is enabled, and retained only as long as the device is in System ON mode. See POWER Power supply on
page 78 for more information about power modes. When the peripheral is disabled, the pins will behave as
regular GPIOs, and use the configuration in their respective OUT bit field and PIN_CNF[n] register.
To ensure correct behaviour in the PDM module, the pins used by the PDM module must be configured in
the GPIO peripheral as described in Table 102: GPIO configuration before enabling peripheral on page
440 before enabling the PDM module. This is to ensure that the pins used by the PDM module are driven
correctly if the PDM module itself is temporarily disabled or the device temporarily enters System OFF. This
configuration must be retained in the GPIO for the selected I/Os as long as the PDM module is supposed to
be connected to an external PDM circuit.
Only one peripheral can be assigned to drive a particular GPIO pin at a time. Failing to do so may result in
unpredictable behaviour.
Table 102: GPIO configuration before enabling peripheral
PDM signal
PDM pin
Direction
Output value Comment
CLK
As specified in PSEL.CLK
Output
0
DIN
As specified in PSEL.DIN
Input
Not applicable
43.7 Registers
Table 103: Instances
Base address Peripheral
Instance
Description
Configuration
0x4001D000 PDM
PDM
Pulse Density Modulation (Digital
Microphone Interface)
Table 104: Register Overview
Register
Offset
Description
TASKS_START
0x000
Starts continuous PDM transfer
TASKS_STOP
0x004
Stops PDM transfer
EVENTS_STARTED
0x100
PDM transfer has started
EVENTS_STOPPED
0x104
PDM transfer has finished
EVENTS_END
0x108
The PDM has written the last sample specified by SAMPLE.MAXCNT (or the last sample after a STOP
task has been received) to Data RAM
INTEN
0x300
Enable or disable interrupt
INTENSET
0x304
Enable interrupt
INTENCLR
0x308
Disable interrupt
ENABLE
0x500
PDM module enable register
PDMCLKCTRL
0x504
PDM clock generator control
MODE
0x508
Defines the routing of the connected PDM microphones' signals
GAINL
0x518
Left output gain adjustment
GAINR
0x51C
Right output gain adjustment
PSEL.CLK
0x540
Pin number configuration for PDM CLK signal
PSEL.DIN
0x544
Pin number configuration for PDM DIN signal
SAMPLE.PTR
0x560
RAM address pointer to write samples to with EasyDMA
SAMPLE.MAXCNT
0x564
Number of samples to allocate memory for in EasyDMA mode
43.7.1 INTEN
Address offset: 0x300
Enable or disable interrupt