Add z180 port - sdcc & sccz80 compiler support (#5)

This was originally contributed here - https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/52

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

3 files changed, 727 insertions, 0 deletions

diff --git a/Z88DK/Z180/port.c b/Z88DK/Z180/port.c
new file mode 100644
index 0000000..59a815f
--- /dev/null
+++ b/Z88DK/Z180/port.c
@@ -0,0 +1,283 @@
+/*
+ * FreeRTOS Kernel V10.4.3
+ * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+
+#include <stdlib.h>
+
+#include "include/FreeRTOS.h"
+
+#if __SDCC
+#include "include/sdcc/task.h"
+#elif __SCCZ80
+#include "include/sccz80/task.h"
+#endif
+
+/*-----------------------------------------------------------*/
+
+/* We require the address of the pxCurrentTCB variable, but don't want to know
+any details of its type. */
+
+typedef void TCB_t;
+extern volatile TCB_t * volatile pxCurrentTCB;
+/*-----------------------------------------------------------*/
+
+/*
+ * Macro to save all the general purpose registers, the save the stack pointer
+ * into the TCB.
+ *
+ * The first thing we do is save the flags then disable interrupts. This is to
+ * guard our stack against having a context switch interrupt after we have already
+ * pushed the registers onto the stack.
+ *
+ * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
+ * so we need not worry about reading/writing to the stack pointer.
+ */
+
+#define configTICK_RATE_HZ              (256)               /* Timer configured */
+#define configISR_ORG                   ASMPC               /* ISR relocation */
+#define configISR_IVT                   0xFFE6              /* PRT1 address */
+
+#ifdef __SCCZ80
+
+#define configSETUP_TIMER_INTERRUPT()                           \
+    do{                                                         \
+        asm(                                                    \
+            "EXTERN __CPU_CLOCK                             \n" \
+            "EXTERN RLDR1L, RLDR1H                          \n" \
+            "EXTERN TCR, TCR_TIE1, TCR_TDE1                 \n" \
+            "ld de,_timer_isr                               \n" \
+            "ld hl,"string(configISR_IVT)" ; PRT1 address   \n" \
+            "ld (hl),e                                      \n" \
+            "inc hl                                         \n" \
+            "ld (hl),d                                      \n" \
+            "; we do configTICK_RATE_HZ ticks per second    \n" \
+            "ld hl,__CPU_CLOCK/"string(configTICK_RATE_HZ)"/20-1 \n" \
+            "out0(RLDR1L),l                                 \n" \
+            "out0(RLDR1H),h                                 \n" \
+            "in0 a,(TCR)                                    \n" \
+            "or TCR_TIE1|TCR_TDE1                           \n" \
+            "out0 (TCR),a                                   \n" \
+            );                                                  \
+    }while(0)
+
+#define configRESET_TIMER_INTERRUPT()                           \
+    do{                                                         \
+        asm(                                                    \
+            "EXTERN TCR, TMDR1L                             \n" \
+            "in0 a,(TCR)                                    \n" \
+            "in0 a,(TMDR1L)                                 \n" \
+            );                                                  \
+    }while(0)
+
+#define configSTOP_TIMER_INTERRUPT()                            \
+    do{                                                         \
+        asm(                                                    \
+            "EXTERN TCR, TCR_TIE1, TCR_TDE1                 \n" \
+            "; disable down counting and interrupts for PRT1\n" \
+            "in0 a,(TCR)                                    \n" \
+            "xor TCR_TIE1|TCR_TDE1                          \n" \
+            "out0 (TCR),a                                   \n" \
+            );                                                  \
+    }while(0)
+
+#endif
+
+#ifdef __SDCC
+
+#define configSETUP_TIMER_INTERRUPT()                           \
+    do{                                                         \
+        __asm                                                   \
+            EXTERN __CPU_CLOCK                                  \
+            EXTERN RLDR1L, RLDR1H                               \
+            EXTERN TCR, TCR_TIE1, TCR_TDE1                      \
+            ; address of ISR                                    \
+            ld de,_timer_isr                                    \
+            ld hl,configISR_IVT ; PRT1 address                  \
+            ld (hl),e                                           \
+            inc hl                                              \
+            ld (hl),d                                           \
+            ; we do configTICK_RATE_HZ ticks per second         \
+            ld hl,__CPU_CLOCK/configTICK_RATE_HZ/20-1           \
+            out0(RLDR1L),l                                      \
+            out0(RLDR1H),h                                      \
+            ; enable down counting and interrupts for PRT1      \
+            in0 a,(TCR)                                         \
+            or TCR_TIE1|TCR_TDE1                                \
+            out0 (TCR),a                                        \
+        __endasm;                                               \
+    }while(0)
+
+#define configRESET_TIMER_INTERRUPT()                           \
+    do{                                                         \
+        __asm                                                   \
+            EXTERN TCR, TMDR1L                                  \
+            ; reset interrupt for PRT1                          \
+            in0 a,(TCR)                                         \
+            in0 a,(TMDR1L)                                      \
+        __endasm;                                               \
+    }while(0)
+
+#define configSTOP_TIMER_INTERRUPT()                            \
+    do{                                                         \
+        __asm                                                   \
+            EXTERN TCR, TCR_TIE1, TCR_TDE1                      \
+            ; disable down counting and interrupts for PRT1     \
+            in0 a,(TCR)                                         \
+            xor TCR_TIE1|TCR_TDE1                               \
+            out0 (TCR),a                                        \
+        __endasm;                                               \
+    }while(0)
+
+#endif
+
+/*-----------------------------------------------------------*/
+
+/*
+ * Perform hardware setup to enable ticks from Timer.
+ */
+static void prvSetupTimerInterrupt( void ) __preserves_regs(iyh,iyl);
+/*-----------------------------------------------------------*/
+
+/*
+ * See header file for description.
+ */
+StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
+{
+    /* Place the parameter on the stack in the expected location. */
+    *pxTopOfStack-- = ( StackType_t ) pvParameters;
+
+    /* Place the task return address on stack. Not used */
+    *pxTopOfStack-- = ( StackType_t ) 0;
+
+    /* The start of the task code will be popped off the stack last, so place
+    it on first. */
+    *pxTopOfStack-- = ( StackType_t ) pxCode;
+
+    /* Now the registers. */
+    *pxTopOfStack-- = ( StackType_t ) 0xAFAF;   /* AF  */
+    *pxTopOfStack-- = ( StackType_t ) 0x0404;   /* IF  */
+    *pxTopOfStack-- = ( StackType_t ) 0xBCBC;   /* BC  */
+    *pxTopOfStack-- = ( StackType_t ) 0xDEDE;   /* DE  */
+    *pxTopOfStack-- = ( StackType_t ) 0xEFEF;   /* HL  */
+    *pxTopOfStack-- = ( StackType_t ) 0xFAFA;   /* AF' */
+    *pxTopOfStack-- = ( StackType_t ) 0xCBCB;   /* BC' */
+    *pxTopOfStack-- = ( StackType_t ) 0xEDED;   /* DE' */
+    *pxTopOfStack-- = ( StackType_t ) 0xFEFE;   /* HL' */
+    *pxTopOfStack-- = ( StackType_t ) 0xCEFA;   /* IX  */
+    *pxTopOfStack   = ( StackType_t ) 0xADDE;   /* IY  */
+
+    return pxTopOfStack;
+}
+/*-----------------------------------------------------------*/
+
+BaseType_t xPortStartScheduler( void ) __preserves_regs(a,b,c,d,e,iyh,iyl) __naked
+{
+    /* Setup the relevant timer hardware to generate the tick. */
+    prvSetupTimerInterrupt();
+
+    /* Restore the context of the first task that is going to run. */
+    portRESTORE_CONTEXT();
+
+    /* Should not get here. */
+    return pdFALSE;
+}
+/*-----------------------------------------------------------*/
+
+void vPortEndScheduler( void ) __preserves_regs(b,c,d,e,h,l,iyh,iyl)
+{
+    /*
+     * It is unlikely that the Z80 port will get stopped.
+     * If required simply disable the tick interrupt here.
+     */
+    configSTOP_TIMER_INTERRUPT();
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Manual context switch.  The first thing we do is save the registers so we
+ * can use a naked attribute. This is called by the application, so we don't have
+ * to check which bank is loaded.
+ */
+void vPortYield( void ) __preserves_regs(a,b,c,d,e,h,l,iyh,iyl) __naked
+{
+    portSAVE_CONTEXT();
+    vTaskSwitchContext();
+    portRESTORE_CONTEXT();
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Manual context switch callable from ISRs. The first thing we do is save
+ * the registers so we can use a naked attribute.
+ */
+void vPortYieldFromISR(void)  __preserves_regs(a,b,c,d,e,h,l,iyh,iyl) __naked
+void vPortYieldFromISR(void)
+{
+    portSAVE_CONTEXT_IN_ISR();
+    vTaskSwitchContext();
+    portRESTORE_CONTEXT_IN_ISR();
+}
+/*-----------------------------------------------------------*/
+
+/*
+ * Initialize Timer (PRT1 for YAZ180, and SCZ180 HBIOS).
+ */
+void prvSetupTimerInterrupt( void ) __preserves_regs(iyh,iyl)
+{
+    configSETUP_TIMER_INTERRUPT();
+}
+/*-----------------------------------------------------------*/
+
+void timer_isr(void) __preserves_regs(a,b,c,d,e,h,l,iyh,iyl) __naked
+{
+#if configUSE_PREEMPTION == 1
+    /*
+     * Tick ISR for preemptive scheduler.  We can use a naked attribute as
+     * the context is saved at the start of timer_isr().  The tick
+     * count is incremented after the context is saved.
+     *
+     * Context switch function used by the tick.  This must be identical to
+     * vPortYield() from the call to vTaskSwitchContext() onwards.  The only
+     * difference from vPortYield() is the tick count is incremented as the
+     * call comes from the tick ISR.
+     */
+    portSAVE_CONTEXT_IN_ISR();
+    configRESET_TIMER_INTERRUPT();
+    xTaskIncrementTick();
+    vTaskSwitchContext();
+    portRESTORE_CONTEXT_IN_ISR();
+#else
+    /*
+     * Tick ISR for the cooperative scheduler.  All this does is increment the
+     * tick count.  We don't need to switch context, this can only be done by
+     * manual calls to taskYIELD();
+     */
+    portSAVE_CONTEXT_IN_ISR();
+    configRESET_TIMER_INTERRUPT();
+    xTaskIncrementTick();
+    portRESTORE_CONTEXT_IN_ISR();
+#endif
+} // configUSE_PREEMPTION
diff --git a/Z88DK/Z180/portmacro.h b/Z88DK/Z180/portmacro.h
new file mode 100644
index 0000000..f8f2f02
--- /dev/null
+++ b/Z88DK/Z180/portmacro.h
@@ -0,0 +1,431 @@
+/*
+ * FreeRTOS Kernel V10.4.3
+ * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+#ifndef PORTMACRO_H
+#define PORTMACRO_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*-----------------------------------------------------------
+ * Port specific definitions.
+ *
+ * The settings in this file configure FreeRTOS correctly for the
+ * given Z80 (Z180, Z80N) hardware and SCCZ80 or SDCC compiler.
+ *
+ * These settings should not be altered.
+ *-----------------------------------------------------------
+ */
+
+/* Type definitions. */
+#define portCHAR                    char
+#define portFLOAT                   float
+#define portDOUBLE                  double
+#define portLONG                    long
+#define portSHORT                   int
+
+typedef uint16_t StackType_t;
+typedef int8_t BaseType_t;
+typedef uint8_t UBaseType_t;
+
+#if configUSE_16_BIT_TICKS == 1
+    typedef uint16_t TickType_t;
+    #define portMAX_DELAY ( TickType_t ) 0xffff
+#else
+    typedef uint32_t TickType_t;
+    #define portMAX_DELAY ( TickType_t ) 0xffffffffUL
+#endif
+/*-----------------------------------------------------------*/
+
+/* General purpose stringify macros. */
+
+#define string(a) __string(a)
+#define __string(a) #a
+/*-----------------------------------------------------------*/
+
+/* Critical section management using sccz80 compiler. */
+
+#ifdef __SCCZ80
+
+#define portENTER_CRITICAL()        \
+    do{                             \
+        asm(                        \
+            "ld a,i             \n" \
+            "di                 \n" \
+            "push af            \n" \
+            );                      \
+    }while(0)
+
+#define portEXIT_CRITICAL()         \
+    do{                             \
+        asm(                        \
+            "pop af             \n" \
+            "; di    ; unneeded \n" \
+            "jp PO,ASMPC+4      \n" \
+            "ei                 \n" \
+            );                      \
+    }while(0)
+
+#define portDISABLE_INTERRUPTS()    \
+    do{                             \
+        asm(                        \
+            "di                 \n" \
+            );                      \
+    }while(0)
+
+#define portENABLE_INTERRUPTS()     \
+    do{                             \
+        asm(                        \
+            "ei                 \n" \
+            );                      \
+    }while(0)
+
+#define portNOP()                   \
+    do{                             \
+        asm(                        \
+            "nop                \n" \
+            );                      \
+    }while(0)
+
+/*
+ * Macros to save all the registers, and save the stack pointer into the TCB.
+ */
+
+#define portSAVE_CONTEXT()          \
+    do{                             \
+        asm(                        \
+            "push af            \n" \
+            "ld a,i             \n" \
+            "di                 \n" \
+            "push af ; iff1:iff2\n" \
+            "push bc            \n" \
+            "push de            \n" \
+            "push hl            \n" \
+            "exx                \n" \
+            "ex af,af           \n" \
+            "push af            \n" \
+            "push bc            \n" \
+            "push de            \n" \
+            "push hl            \n" \
+            "push ix            \n" \
+            "push iy            \n" \
+            "ld hl,0            \n" \
+            "add hl,sp          \n" \
+            "ld de,(_pxCurrentTCB)  \n"\
+            "ex de,hl           \n" \
+            "ld (hl),e          \n" \
+            "inc hl             \n" \
+            "ld (hl),d          \n" \
+            );                      \
+    }while(0)
+
+#define portRESTORE_CONTEXT()       \
+    do{                             \
+        asm(                        \
+            "ld hl,(_pxCurrentTCB)  \n" \
+            "ld e,(hl)          \n" \
+            "inc hl             \n" \
+            "ld d,(hl)          \n" \
+            "ex de,hl           \n" \
+            "ld sp,hl           \n" \
+            "pop iy             \n" \
+            "pop ix             \n" \
+            "pop hl             \n" \
+            "pop de             \n" \
+            "pop bc             \n" \
+            "pop af             \n" \
+            "ex af,af           \n" \
+            "exx                \n" \
+            "pop hl             \n" \
+            "pop de             \n" \
+            "pop bc             \n" \
+            "pop af  ; iff1:iff2\n" \
+            "; di    ; unneeded \n" \
+            "jp PO,ASMPC+4      \n" \
+            "ei                 \n" \
+            "pop af             \n" \
+            "ret                \n" \
+            );                      \
+    }while(0)
+
+#define portSAVE_CONTEXT_IN_ISR()   \
+    do{                             \
+        asm(                        \
+            "PHASE "string(configISR_ORG)"  \n" \
+            "._timer_isr_start  \n" \
+            "push af            \n" \
+            "ld a,0x7F          \n" \
+            "inc a   ; set PE   \n" \
+            "push af ; iff1:iff2\n" \
+            "push bc            \n" \
+            "push de            \n" \
+            "push hl            \n" \
+            "exx                \n" \
+            "ex af,af           \n" \
+            "push af            \n" \
+            "push bc            \n" \
+            "push de            \n" \
+            "push hl            \n" \
+            "push ix            \n" \
+            "push iy            \n" \
+            "ld hl,0            \n" \
+            "add hl,sp          \n" \
+            "ld de,(_pxCurrentTCB)  \n" \
+            "ex de,hl           \n" \
+            "ld (hl),e          \n" \
+            "inc hl             \n" \
+            "ld (hl),d          \n" \
+            );                      \
+    }while(0)
+
+#define portRESTORE_CONTEXT_IN_ISR()\
+    do{                             \
+        asm(                        \
+            "ld hl,(_pxCurrentTCB)  \n" \
+            "ld e,(hl)          \n" \
+            "inc hl             \n" \
+            "ld d,(hl)          \n" \
+            "ex de,hl           \n" \
+            "ld sp,hl           \n" \
+            "pop iy             \n" \
+            "pop ix             \n" \
+            "pop hl             \n" \
+            "pop de             \n" \
+            "pop bc             \n" \
+            "pop af             \n" \
+            "ex af,af           \n" \
+            "exx                \n" \
+            "pop hl             \n" \
+            "pop de             \n" \
+            "pop bc             \n" \
+            "pop af  ; iff1:iff2\n" \
+            "; di    ; unneeded \n" \
+            "jp PO,ASMPC+4      \n" \
+            "ei                 \n" \
+            "pop af             \n" \
+            "reti               \n" \
+            "._timer_isr_end    \n" \
+            "DEPHASE            \n" \
+            );                      \
+    }while(0)
+
+#endif
+/*-----------------------------------------------------------*/
+
+/* Critical section management using sdcc compiler. */
+
+#ifdef __SDCC
+
+#define portENTER_CRITICAL()        \
+    do{                             \
+        __asm                       \
+            ld a,i                  \
+            di                      \
+            push af                 \
+        __endasm;                   \
+    }while(0)
+
+#define portEXIT_CRITICAL()         \
+    do{                             \
+        __asm                       \
+            pop af                  \
+            ; di    ; unneeded      \
+            jp PO,ASMPC+4           \
+            ei                      \
+        __endasm;                   \
+    }while(0)
+
+#define portDISABLE_INTERRUPTS()    \
+    do{                             \
+        __asm                       \
+            di                      \
+        __endasm;                   \
+    }while(0)
+
+#define portENABLE_INTERRUPTS()     \
+    do{                             \
+        __asm                       \
+            ei                      \
+        __endasm;                   \
+    }while(0)
+
+#define portNOP()                   \
+    do{                             \
+        __asm                       \
+            nop                     \
+        __endasm;                   \
+    }while(0)
+
+/*
+ * Macros to save all the registers, and save the stack pointer into the TCB.
+ */
+
+#define portSAVE_CONTEXT()          \
+    do{                             \
+        __asm                       \
+            push af                 \
+            ld a,i                  \
+            di                      \
+            push af ; iff1:iff2     \
+            push bc                 \
+            push de                 \
+            push hl                 \
+            exx                     \
+            ex af,af                \
+            push af                 \
+            push bc                 \
+            push de                 \
+            push hl                 \
+            push ix                 \
+            push iy                 \
+            ld hl,0                 \
+            add hl,sp               \
+            ld de,(_pxCurrentTCB)   \
+            ex de,hl                \
+            ld (hl),e               \
+            inc hl                  \
+            ld (hl),d               \
+        __endasm;                   \
+    }while(0)
+
+#define portRESTORE_CONTEXT()       \
+    do{                             \
+        __asm                       \
+            ld hl,(_pxCurrentTCB)   \
+            ld e,(hl)               \
+            inc hl                  \
+            ld d,(hl)               \
+            ex de,hl                \
+            ld sp,hl                \
+            pop iy                  \
+            pop ix                  \
+            pop hl                  \
+            pop de                  \
+            pop bc                  \
+            pop af                  \
+            ex af,af                \
+            exx                     \
+            pop hl                  \
+            pop de                  \
+            pop bc                  \
+            pop af  ; iff1:iff2     \
+            ; di    ; unneeded      \
+            jp PO,ASMPC+4           \
+            ei                      \
+            pop af                  \
+            ret                     \
+        __endasm;                   \
+    }while(0)
+
+#define portSAVE_CONTEXT_IN_ISR()   \
+    do{                             \
+        __asm                       \
+            PHASE configISR_ORG     \
+            _timer_isr_start:       \
+            push af                 \
+            ld a,0x7F               \
+            inc a   ; set PE        \
+            push af ; iff1:iff2     \
+            push bc                 \
+            push de                 \
+            push hl                 \
+            exx                     \
+            ex af,af                \
+            push af                 \
+            push bc                 \
+            push de                 \
+            push hl                 \
+            push ix                 \
+            push iy                 \
+            ld hl,0                 \
+            add hl,sp               \
+            ld de,(_pxCurrentTCB)   \
+            ex de,hl                \
+            ld (hl),e               \
+            inc hl                  \
+            ld (hl),d               \
+        __endasm;                   \
+    }while(0)
+
+#define portRESTORE_CONTEXT_IN_ISR()\
+    do{                             \
+        __asm                       \
+            ld hl,(_pxCurrentTCB)   \
+            ld e,(hl)               \
+            inc hl                  \
+            ld d,(hl)               \
+            ex de,hl                \
+            ld sp,hl                \
+            pop iy                  \
+            pop ix                  \
+            pop hl                  \
+            pop de                  \
+            pop bc                  \
+            pop af                  \
+            ex af,af                \
+            exx                     \
+            pop hl                  \
+            pop de                  \
+            pop bc                  \
+            pop af  ; iff1:iff2     \
+            ; di    ; unneeded      \
+            jp PO,ASMPC+4           \
+            ei                      \
+            pop af                  \
+            reti                    \
+            _timer_isr_end:         \
+            DEPHASE                 \
+        __endasm;                   \
+    }while(0)
+
+#endif
+/*-----------------------------------------------------------*/
+
+/* Architecture specifics. */
+
+#define portSTACK_GROWTH            ( -1 )
+#define portTICK_PERIOD_MS          ( ( TickType_t ) 1000 / configTICK_RATE_HZ )
+#define portBYTE_ALIGNMENT          1
+/*-----------------------------------------------------------*/
+
+/* Kernel utilities. */
+extern void vPortYield( void );
+#define portYIELD()                 vPortYield()
+
+extern void vPortYieldFromISR( void );
+#define portYIELD_FROM_ISR()        vPortYieldFromISR()
+/*-----------------------------------------------------------*/
+
+/* Task function macros as described on the FreeRTOS.org WEB site. */
+#define portTASK_FUNCTION_PROTO( vFunction, pvParameters ) void vFunction( void *pvParameters )
+#define portTASK_FUNCTION( vFunction, pvParameters ) void vFunction( void *pvParameters )
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PORTMACRO_H */
diff --git a/Z88DK/Z180/readme.md b/Z88DK/Z180/readme.md
new file mode 100644
index 0000000..89af17a
--- /dev/null
+++ b/Z88DK/Z180/readme.md
@@ -0,0 +1,13 @@
+<h1>z180 support</h1>
+
+Description
+-----------
+This PR establishes support for a Zilog z180 port, using the Programmable Reload Timer 1, configured at 256 Hz.
+
+Because of the generality of the z180, the address of the Interrupt Vector for PRT1 is configurable, and must be configured by the `crt0.asm` outside of this port. A configuration assumption has been made.
+
+The two compilers ([used by the z88dk](https://github.com/z88dk/z88dk)) are supported. The sccz80 compiler and the sdcc compiler. The PR is located under Z88dk.
+
+Background
+-----------
+This PR is based on running code for the [SC130](https://smallcomputercentral.wordpress.com/sc130-z180-motherboard/)/[SC131](https://smallcomputercentral.wordpress.com/sc131-z180-pocket-computer/) and [YAZ180](https://github.com/feilipu/yaz180) platforms, and is maintained by the z88dk team in this [z88dk-libraries](https://github.com/feilipu/z88dk-libraries/tree/master/freertos) repository.