mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 406

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

Rapid GPIO (RGPIO)
17.4
The RGPIO module is a relatively-simple design with its behavior controlled by the program-visible
registers defined within its programming model.
The RGPIO module is connected to the processor’s local two-stage pipelined bus with the stages of the
ColdFire core’s operand execution pipeline (OEP) mapped directly onto the bus. This structure allows the
processor access to the RGPIO module for single-cycle pipelined reads and writes with a zero wait-state
response (as viewed in the system bus data phase stage).
17.5
The reset state of the RGPIO module disables the entire 16-bit data port. Prior to using the RGPIO port,
software typically:
17.6
This section examines the relative performance of the RGPIO output pins for two simple applications
In both applications, the relative speed of the GPIO output is presented as a function of the location of the
output bit (RGPIO versus peripheral bus GPIO).
17.6.1
In this example, several different instruction loops are executed, each generating a square-wave output
with a 50% duty cycle. For this analysis, the executed code is mapped into the processor’s RAM. This
configuration is selected to remove any jitter from the output square wave caused by the limitations
defined by the two-cycle flash memory accesses and restrictions on the initiation of a flash access. The
following instruction loops were studied:
17-8
Field
15–0
TOG
•
•
•
•
•
•
Enables the appropriate pins in RGPIO_ENB
Configures the pin direction in RGPIO_DIR
Defines the contents of the data register (RGPIO_DATA)
The processor executes a loop to toggle an output pin for a specific number of cycles, producing a
square-wave output
The processor transmits a 16-bit message using a three-pin SPI-like interface with a serial clock,
serial chip select, and serial data bit.
BCHG_LOOP — In this loop, a bit change instruction was executed using the GPIO data byte as
the operand. This instruction performs a read-modify-write operation and inverts the addressed bit.
RGPIO toggle data.
0 No effect
1 Inverts the corresponding bit in RGPIO_DATA
Functional Description
Initialization Information
Application Information
Application 1: Simple Square-Wave Generation
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Table 17-10. RGPIO_TOG Field Descriptions
Description
Freescale Semiconductor