6.4.1. Headers and Constant Definitions

The header files for TLM 2.0 and the simple target convenience socket are included.

#include "tlm.h"
#include "tlm_utils/simple_target_socket.h"

Convenience constants for the address mask, named register offsets and bit fields are then defined. The address mask is needed, since in this simple SoC model there is no arbiter/decoder to strip out the higher order bits from the address before the transaction is sent to the UART.

#define UART_ADDR_MASK      7     // Mask for addresses (3 bit bus)

Named constants are defined giving the address offset of each register of the UART

#define UART_BUF  0               // R/W: Rx/Tx buffer, DLAB=0
#define UART_IER  1             // R/W: Interrupt Enable Register, DLAB=0
#define UART_IIR  2             // R: Interrupt ID Register
#define UART_LCR  3             // R/W: Line Control Register
#define UART_MCR  4             // W: Modem Control Register
#define UART_LSR  5             // R: Line Status Register
#define UART_MSR  6             // R: Modem Status Register
#define UART_SCR  7             // R/W: Scratch Register

Bit masks are declared for each of the bits and bit fields of interest in the UART. For example the interrupt identification register needs a mask for the pending bit of a mask for the two bits representing the highest priority interrupt and a mask for each possible interrupt.

#define UART_IIR_IPEND  0x01    // Interrupt pending (active low)

#define UART_IIR_MASK   0x06    // the IIR status bits
#define UART_IIR_RLS    0x06    // Receiver line status
#define UART_IIR_RDA    0x04    // Receiver data available
#define UART_IIR_THRE   0x02    // Transmitter holding reg empty
#define UART_IIR_MOD    0x00    // Modem status