vSR
#define ADB_SR() read_via_reg(VIA1, vSR)
write_via_reg(VIA1, vSR, adbOutputBuffer[adbSentChars + 1]);
write_via_reg(VIA1, vSR, adbOutputBuffer[adbSentChars + 1]); /* send next byte */
write_via_reg(VIA1, vSR, adbOutputBuffer[adbSentChars + 1]); /* load byte for output */
write_via_reg(VIA1, vSR, data); /* PM_SR() = data; */
#define PM_SR() read_via_reg(VIA1, vSR)